Studies in the Theory of Descent, Volume II

10

[The larvæ of the 110th genus, Paphia, Fabr. (Anæa, Hübn.) are also smoothed-skinned. See Edwards’ figure (loc. cit. vol. i. Pl. XLVI.) of P. Glycerium. Also C. V. Riley’s “Second Annual Report” on the insects of Missouri, 1870, p. 125. Burmeister figures the larva of a species of Prepona (genus 99) which is smooth (P. Demophon, loc. cit. Pl. V. Fig. 1). The horns on the head of Apatura, &c., may possibly be a survival from a former spiny condition. R.M.]

11

“Synopsis of the described Lepidoptera of North America.” Washington, 1862.

12

“Catalog der Lepidopteren des Europäischen Faunengebietes.” Dresden, 1871.

13

This group of moths (“Schwärmer”) is regarded as of very different extents by systematists; when I here comprise under it only the Sphingidæ proper and the Sesiidæ, I by no means ignore the grounds which favour a greater extension of the group; the latter is not rigidly limited. [The affinities of the Sesiidæ (Ægeriidæ) are by no means clearly made out: it appears probable that they are not related to the Sphingidæ. See note 160, p. 370. R.M.]

14

[For Mr. A. G. Butler’s observations on the genus Acronycta, see “Trans. Ent. Soc.” 1879, p. 313; and note 68, p. 169, of the present volume. R.M.]

15

[The following characters are given in Stainton’s “Manual of British Butterflies and Moths,” vol. i. p. 114: – “Larva of very variable form: at one extreme we find the singular Cerura larvæ, with only fourteen legs, and two long projecting tails from the last segment; at the other extreme we have larvæ with sixteen legs and no peculiarity of form, such as Chaonia and Bucephala; most have, however, the peculiarity of holding the hind segment of the body erect when in repose; generally quite naked, though downy in Bucephala and rather hairy in Curtulu; very frequently there are projections on the back of the twelfth segment.” R.M.]

16

Encyl. Meth. ix. p. 310.

17

[The genus Vanessa (in the wide sense) appears to be in a remarkable condition of what may be called phyletic preservation. Thus, the group of species allied to V. C. – album passes by almost insensible steps into the group of butterflies typified by our “Tortoiseshells.” The following is a list of some of the intermediate species in their transitional order: —I. – album, V. – album, Faunus, Comma, California, Dryas, Polychloros, Xanthomelas, Cashmirensis, Urticæ, Milberti, &c. Similarly, our Atalanta and Cardui are connected by a number of intermediate forms, showing a complete transition from the one to the other. The following is the order of the species so far as I am acquainted with them: —Atalanta, Dejeanii, Callirhoë, Tammeamea, Myrinna, Huntera, Terpsichore, Carye, Kershawii, and Cardui. R.M.]

18

“Prodromus Systematis Lepidopterorum.” Regensburg, 1864.

19

[The larva of Acherontia Morta, figured by Butler (see note 121, p. 262), possesses the characteristically recurved horn; that of Ach. Medusa figured by the same author, does not appear to possess this character in any marked degree. R.M.]

20

[See note 97, p. 233. R.M.]

21

Loc. cit. Pl. XXV. [This species is referred by Butler to the genus Paonias, Hübn. R.M.]

22

Abbot and Smith, Pl. XXIX. [Placed by Butler in the genus Cressonia, Grote and Robinson. Abbot and Smith state that this larva is sometimes green. According to Mr. Herman Strecker (Lepidop. Rhopal. and Hetero, Reading, Pa. 1874, p. 54) it feeds upon black walnut (Juglans Nigra), hickory (Carya Alba), and ironwood (Ostrya Virginica). Of the North American species of Smerinthus, the following, in addition to Excæcatus, closely resemble our Ocellatus: —S. (Calasymbolus) Geminatus, Say; (C.) Cerisii, Kirby; and Ophthalmicus, Boisd. In addition to S. (Cressonia) Juglandis, S. (Triptogon) Modesta much resembles our Populi. The larva of Geminatus, according to Strecker, is “pale green, lightest above, with yellow lateral granulated stripes; caudal horn violet; stigmata red. It feeds on the willow.” R.M.]

23

Cat. Brit. Mus.

24

[This lengthening of the true legs is mimetic according to Hermann Müller, and causes the anterior portion of the caterpillar to resemble a spider. See note 129, p. 290. R.M.]

25

[Certain butterflies appear to be crepuscular, if not nocturnal in their habits. Thus in his “Notes on the Lepidoptera of Natal,” Mr. W. D. Gooch states that he never saw Melanitis, Leda, or Gnophodes Parmeno on the wing by day, but generally during the hour after sunset. He adds: – “My sugar always attracted them freely, even up to 10 or 11 p.m.” Many species of Hesperidæ are also stated to be of crepuscular habits by this same observer. See “Entomologist,” vol xvi. pp. 38 and 40. R.M.]

26

I only make this assumption for the sake of simplicity, and not because I am convinced that the existing Rhopalocera are actually the oldest Lepidopterous group.

27

Zeitschrift für wissenschaftl. Zoologie, vol. xx. p. 519.

28

[See for instance Lubbock’s “Origin and Metamorphoses of Insects,” chap. iii.; and F. M. Balfour’s “Comparative Embryology,” vol. i., 1880, pp. 327 – 356. This last work contains an admirable résumé of our knowledge of the embryonic development of insects up to the date of publication. R.M.]

29

Are not the 4th, 11th, and 12th segments destitute of the rudiments of legs as in the larvæ of all existing saw-flies? I might almost infer this from Bütschli’s figures (see for instance Pl. XXV., Fig. 17A).

30

[The grub-formed Hymenopterous larvæ, like the larvæ of all other holometabolous insects, thus represent an acquired degenerative stage in the development, i. e. an adaptation to the conditions of life at that stage. Bearing in mind the above-quoted observations of Bütschli and the caterpillar-like form of the Terebrantiate group of Hymenopterous larvæ, the following remarks of Balfour’s (loc. cit. p. 353), appear highly suggestive: – “While in a general way it is clear that the larval forms of insects cannot be expected to throw much light on the nature of insect ancestors, it does nevertheless appear to me probable that such forms as the caterpillars of the Lepidoptera are not without a meaning in this respect. It is easy to conceive that even a secondary larval form may have been produced by the prolongation of one of the embryonic stages; and the general similarity of a caterpillar to Peripatus, and the retention by it of post-thoracic appendages, are facts which appear to favour this view of the origin of the caterpillar form.” See also Sir John Lubbock, loc. cit., pp. 93 and 95. R.M.]

31

[In the most recent works dealing with this order six groups, based on the character of the imagines are recognized, viz.: —Tubulifera, Terebrantia, Pupivora, Heterogyna Fossores, and Mellifera. (See, for instance, F. P. Pascoe’s “Zoological Classification,” 2nd ed. p. 147.) Of these groups the larvæ of the Terebrantia as thus restricted are all of the caterpillar type (Tenthredinidæ and Siricidæ), whilst those of the other groups are maggot-shaped. For a description of the development of the remarkable aberrant larva of Platygaster, see Ganin in Zeit. f. wissenschaftl. Zool., vol. xix. 1869. R.M.]

32

[For recent investigations on the structure of the thorax in Diptera, see a paper by Mr. A. Hammond, in Journ. Linn. Soc., Zoology, vol xv. p. 9. R.M.]

33

I am familiar with the fact that the two sub-orders of true Diptera, the short-horned (Brachycera), and the long-horned (Nemocera), are not sharply limited; and I am likewise well acquainted with the circumstance that there are forms which connect the two larval types. The connecting forms of the imagines do not, however, always coincide with the intermediate larval forms, so that there here arises a second and very striking incongruence of morphological relationship which depends only upon the circumstance that the one stage has diverged in form more widely than the other through a greater divergence in the conditions of life. The difficulty is in these cases aggravated because an apparent is added to the true form-relationship through convergence, so that without going into exact details the form and genealogical relationships of the Diptera cannot be distinguished. It would be of great interest for other reasons to make this investigation, and I hope to be able to find leisure for this purpose at some future period.

34

“Entwicklung der Dipteren.” Leipzig, 1864.

35

Lubbock concludes from the presence of thoracic legs in the embryonic larva of bees that these have been derived from a larva of the Campodea type, but he overlooks the fact that the rudiments of the abdominal legs are also present; loc. cit., p. 28.

36

“Für Darwin,” Leipzig, 1864, p. 8.

37

Mem. Peabody Acad. of Science, vol. i. No. 3.

38

Verhandl. Wien. Zoolog. Botan. Gesellsch. 1869, p. 310.

39

Über Ontogenie und Phylogenie der Insekten. Eine akademische Preisschrift. Jen. Zeitschrift. Bd. x. Neue Folge, iii. Heft 2. 1876. [Some remarks by F. M. Balfour on the origin of certain larval forms have already been quoted in a previous note (p. 485). This author further states: – “The fact that in a majority of instances it is possible to trace an intimate connection between the surroundings of a larva and its organization proves in the clearest way that the characters of the majority of existing larval forms of insects have owed their origin to secondary adaptations. A few instances will illustrate this point: – In the simplest types of metamorphosis, e. g. those of the Orthoptera genuina, the larva has precisely the same habits as the adult. We find that a caterpillar form is assumed by phytophagous larvæ amongst the Lepidoptera, Hymenoptera, and Coleoptera. Where the larva has not to go in search of its nutriment the grub-like apodous form is assumed. The existence of such an apodous larva is especially striking in the Hymenoptera, in that rudiments of thoracic and abdominal appendages are present in the embryo and disappear again in the larva… It follows from the above that the development of such forms as the Orthoptera genuina is more primitive than that of the holometabolous forms, &c.” Comparative Embryology, vol. 1, p. 352. R.M.]

40

[The Aphaniptera are now recognized in this country as a sub-order of Diptera. See, for instance, Huxley’s “Anatomy of Invertebrated Animals,” p. 425, and Pascoe’s “Zoological Classification,” 2nd ed. p. 122. R.M.]

41

[This illustration of course only applies to the old arrangement of the Hymenoptera into Terebrantia and Aculeata. See also note 201, p. 488. R.M.]

42

[Eng. ed. This law is perhaps a little too restricted, inasmuch as it is theoretically conceivable that the organism may be able to adapt itself to similar conditions of life in different ways; differences of form could thus depend sometimes upon differences of adaptation and not upon differences in the conditions of life, or, as I have formerly expressed it, it is not necessary to allow always only one best mode of adaptation.]

43

[It must be understood that the word rendered here and elsewhere throughout this work as “transformation” is not to be taken in the narrow sense of metamorphosis, but as having the much broader meaning of a change of any kind incurred by an organism. Metamorphosis is in fact but one phase of transformation. R.M.]

44

By the Editor.

45

Mr. C. V. Riley in his excellent “Annual Reports” already quoted in previous notes, states that the larvæ of Agrotis Inermis, Leucania Unipuncta (Army-worm), and L. Albilinea are all loopers when newly hatched. (See First Report, p. 73; Eighth Report, p. 184; and Ninth Report, p. 53.)

46

The following species not referred to in the previous part of this work are figured by Semper (Beit. zur Entwicklungsgeschichte einiger ostasiat. Schmet.; Verhandl. d. k.k. zoo. bot. Gesell. in Wien, 1867): —Panacra Scapularis, Walk.; Chærocampa Clotho, Drury; and Diludia (Macrosila) Discistriga, Walk. The following are figured by Boisduval and Guenée. (Spéc. Gén. 1874): —Smerinthus Ophthalmicus, Boisd.; Sphinx Jasminearum, Boisd.; S. (Hyloicus) Plebeia, Fabr.; S. (Hyloicus) Cupressi, Boisd.; S. (Pseudosphinx) Catalpæ, Boisd.; Philampelus Jussiuæ, Hübn. (= Sphinx Vitis, Linn.?); and Ceratomia Amyntor, Hübn. As the works of Abbot and Smith, and Horsfield and Moore have been exhausted by Dr. Weismann, it is quite unnecessary to extend this note by giving a list of the species figured by these authors.

47

The same inference has already been drawn with respect to Pterogon (Proserpinus) Œnotheræ, see pp. 257, 258.

48

This would of course be the fourth segment if the head be considered the first, as on the Continent.

49

“Second Annual Report,” 1870, p. 78.

50

“Entomologist,” vol. xiv. p. 7.

51

With reference to the habits of C. Capensis (p. 531), I have since been informed by Mr. Trimen that this species does not conceal itself by day, so that the dimorphism may be regarded as a character retained from an earlier period and adapted to the present life conditions.

52

“Kosmos,” Dec. 1877, p. 218. The paper is here introduced chiefly with a view to illustrate an important case of incongruence among Lepidopterous pupæ.

53

[Maracujá, the local name for the Passiflora. R.M.]

54

See p. 448.

55

Verhandl. Schweiz. Naturforsch. Gesellschaft. Einsiedeln, 1868.

56

[Eng. ed. In 1878 Señor José M. Velasco published a paper entitled “Description, metamorfosis. y costumbres de una especie nueva del genero Siredon.” Memor. Sociedad Mexicana de Historia Natural, December 26th. See Addendum to this essay.]

57

Dana and Silliman’s Amer. Journ., 3rd series, i. p. 89. Annals Nat. Hist. vii. p. 246.

58

Proc. Zoo. Soc. 1870, p. 160.

59

Compt. Rend., vol. lx. p. 765 (1865).

60

Nouvelles Archives du Muséum d’Histoire Nat. Paris, 1866, vol. ii. p. 268.

61

Proc. Boston Soc., vol. xii. p. 97; Silliman’s Amer. Journ., vol. xlvi. p. 364; reference given in “Troschel’s Jahresbericht” for 1868, p. 37.

62

Proc. Boston Soc., vol. xii. p. 97; Silliman’s Amer. Journ., vol. xlvi. p. 364. I have not been able to get a copy of this paper, and quote from a reference in “Troschel’s Jahresbericht.” See preceding note.

63

Dana and Silliman’s Amer. Journ. See note 3.

64

Proc. Acad. Philadelph. xix. 1867, pp. 166–209.

65

Mém. Acad. Petersb. vol. xvi.

66

[Eng. ed. Seidlitz is an exception, since in his work on Parthenogenesis (Leipzig, 1872, p. 13) he states that “In the Axolotl, Pædogenesis, which is not in this case… monogamous, but sexual, and indeed gynækogenetic, has already become so far constant that it has perhaps entirely superseded the orthogenetic reproduction.”]

67

Über den Einfluss der Isolirung auf die Artbildung. Leipzig, 1872, p. 33.

68

Duméril represents the teeth of the vomer as separated from those of the os palatinum by a gap. This is probably accidental, since Gegenbaur (Friedrich u. Gegenbaur, the skull of Axolotl, Würzburg, 1849) figures the rows of teeth as passing over from the one bone to the other without interruption. This was the case with the Axolotls which I have been able to examine on this point; but this small discrepancy is, however, quite immaterial to the question here under consideration.

69

See O. Hertwig “Über das Zahnsystem der Amphibien und seine Bedeutung für die Genese des Skelets der Mundhöhle.” Archiv. für microsc. Anat., vol. xi. Supplement, 1874.

70

[Eng. ed. These Amblystomas have since died and have been minutely described by Dr. Wiedersheim. See his memoir, “Zur Anatomie des Amblystoma Weismanni,” in Zeit. für wiss. Zool., vol. xxxii. p. 216.]

71

See Strauch, loc. cit. p. 10.

72

See Part I. of this volume.

73

[This is the principle of “Degeneration” recognized by Darwin (see “Origin of Species,” 6th ed. p. 389, and “Descent of Man,” vol. i. p. 206), and given fuller expression to by Dr. Anton Dohrn (see his work entitled “Der Ursprung der Wirbelthiere und das Princip des Functionswechsels.” Leipzig, 1875). A large number of cases have been brought together by Prof. E. R. Lankester, in his recent interesting work on “Degeneration, a Chapter in Darwinism.” Nature series, 1880. R.M.]

74

“Sulla Larva del Triton Alpestris.” Archivio per la Zoologia. Genova e Torino, 1861, vol. i. pp. 206–211.

75

See also Lubbock “On the Origin and Metamorphoses of Insects,” London, 1874.

76

See the first essay “On the Seasonal Dimorphism of Butterflies,” p. 82.

77

[Eng. ed. It has frequently been objected to me that the existing Axolotl is not a form resulting from atavism, but a case of “arrested growth.” The expression “atavism” is certainly to be here taken in a somewhat different sense than, for example, in the case of the reversion of the existing Axolotl to the Amblystoma form. Further on, I have myself insisted that in the first case the phyletic stage in which the reversion occurred is still completely preserved in the ontogeny of each individual, whilst the Amblystoma stage has become lost in the ontogeny of the Axolotl. If, therefore, we apply the term “atavism” only to such characters or stages (i. e. complexes of characters) as are no longer preserved in the ontogeny, we cannot thus designate the present arrest of the Axolotl at the perennibranchiate stage. Such a restriction of the word, however, appears to me but little desirable, since the process is identical in both cases, i. e. it depends upon the same law of heredity, in accordance with which a condition formerly occurring as a phyletic stage suddenly reappears through purely internal processes. It is true that the reversion is not complete, i. e. the present sexually mature Axolotl does not correspond in all details with its perennibranchiate ancestors. Since Wiedersheim has shown that the existing Axolotl possesses an intermaxillary gland, this can be safely asserted. This gland occurs only in land Amphibians, and therefore originated with the Amblystoma form, afterwards becoming transferred secondarily to the larval stage. Nevertheless, the present Axolotl must resemble its perennibranchiate ancestors in most other characters, and we should be the more entitled to speak of a reversion to the perennibranchiate stage as we speak also of the reversion of single characters. To this must be added that the Axolotl does not correspond exactly with an Amblystoma larva, since Wiedersheim has shown that the space for the intermaxillary gland is present, but that the gland itself is confined to a few tubes which do not by any means fill up this space. (“Das Kopfskelet der Urodelen.” Morph. Jahrbuch, vol. iii. p. 149). By the expression “arrested growth” not much is said, if at the same time the cause of the arrest is left unstated. But what can be the cause why the whole organization remains stationary at the perennibranchiate stage, the sexual organs only undergoing further development? Surely only that law or force of heredity known by its effects, but obscure with respect to its causes, through which old phyletic stages sometimes suddenly reappear, or in other words, that power through which reversion takes place. It must not be forgotten that all these cases of “larval reproduction” in Amphibians appear suddenly. The present sexually mature form of the Axolotl has not arisen by the sexual maturity gradually receding in the ontogeny from generation to generation, but by the occurrence of single individuals which were sexually mature in the perennibranchiate stage, these having the advantage over the Amblystomæ in the struggle for existence under changed climatic conditions.

By admitting a reversion, we perfectly well explain why arrest at the perennibranchiate stage can be associated with complete development of the sexual organs; the assumption of an “arrested growth” leaves this combination of characters completely unexplained. Moreover, I am of opinion that the expressions “arrested growth” or “reversion” are of but little importance so long as the matter itself is clear.]

78

See Haeckel’s “Anthropogenie,” p. 449.

79

“Der Ursprung der Wirbelthiere und das Princip des Functionswechsels,” Leipzig, 1875.

80

Bull. Soc. Neuchâtel. vol. viii. p. 192. Reference given in “Troschel’s Jahresbericht” for 1869.

81

Sitzungsberichte d. math. phys. Klasse der Akad. d. Wiss. zu München, 1875. Heft i.

82

Compt. Rend. vol. lxviii. pp. 938 and 939.

83

Archiv f. Naturgeschichte, 1867.

84

Compt. Rend. vol. v. 1870, p. 70.

85

Bull. Soc. Neuchâtel. vol. viii. p. 192. Reference given in “Troschel’s Jahresbericht” for 1869.

86

[Eng. ed. It was mentioned in the German edition of this work that in the spring of 1876 a female Amblystoma of the Jardin des Plantes in Paris had laid eggs (see Blanchard in the Compt. Rend. 1876, No. 13, p. 716). Whether these eggs were fertile, or whether they developed was not then made known. Thus much was however at the time clear, that even if this had been the case, the reproduction of this Amblystoma would have been only an exceptional occurrence. At that time there were in the Jardin des Plantes Amblystomas which had been kept for more than ten years, and only on one occasion was there a deposition of eggs, and this by only one specimen. That I was correct in speaking of the “sterility” of these Amblystomas in spite of this one exception, is proved by the latest communication from the Jardin des Plantes. We learn from this (Compt. Rend. No. 14, July, 1879, p. 108) that in the years 1877 and 1878 none of the Amblystomas laid any more eggs, although all means were exerted to bring about propagation. In April, 1879, eggs were again laid by one female, and by a second in May. These eggs certainly developed, as did those of 1876, and produced tadpoles. These Amblystomas are therefore not absolutely, but indeed relatively sterile. Whilst the Axolotl propagates regularly and freely every year, this occurs with the Amblystoma but rarely and sparsely. The degree of their sterility can only be approximately established when we know the number of Amblystomas that have since been kept in the Jardin des Plantes. Unfortunately nothing has been said with respect to this.]