MorpTiology and Pliylogeny of Insects. 449 



8. The embryonic envelopes of tlie Insects probably corre- 

 spond to the remains of a Trochospliere. 



The above theses convey the leading features of my view 

 as to the phylogenetic relations of Insects. Widely different 

 decisions as to the origin of Insects have been pronounced by 

 authors. The hypotheses dealing with the question are 

 enumerated and criticized at some length in Graber's work 

 ' Die Insekten ' * (pp. 66-71) and in Sograf's memoir on the 

 development of Geophilus t, so that I can dispense with a 

 comparison of them. I will merely remark that I entirely 

 agree with Graber's opinion upon the Zooja-hypothesis — " a 

 more unsuitable claimant to be regarded as the ancestor of 

 terrestrial Insects (' einen unpassenderen Landkerfcandi- 

 daten ') could never have been found," — as well as with 

 Sograf's argument against the Myriapod hypothesis of 

 Haeckel \. Quite recently the relationship between Insects 

 and Myriapods has been placed more and more beyond 

 doubt, thanks to the work of Moseley §, Balfour |1, Kennel ^, 

 Sedgwick **, and Gaffron ff upon the anatomy and embryo- 

 logy of FeripatuSj as also to the investigations of Ryder J|, 



* Miinchen, 1877. 



t Sogi'af, " Zur Kenntniss der Embronalentwicklung von Geophilus" 

 Nachr. der Moskauer Gesellscliaft der Freuude der Naturwisseuschaft &c., 

 Bd. 4.S, Lief 1, 1883 (in Russian). 



X Sograf writes : — " Tlie pulli of the Chilognalha correspond to the 

 germinal streak of Insects, provided with six (anterior) pairs of extre- 

 mities Consequently in order that it should be possible to com- 

 pare the Chilognatha with Insects or Arachnids, it would have to be proved 

 that the hexapodous Chilognathaia embryo formerly possessed a far 

 greater number of extremities, all of which atrophied except the three 

 anterior pairs. That such a metamorphosis formerly belonged to the 

 Chilognatha, but was afterwards lost, is very improbable." As we see, 

 the question here also depends upon whether the embryo acquires or loses 

 its legs before or after leavmg the egg. 



§ Moseley, " On the Structure and Development of Peripatus capensis" 

 Phil. Trans. Hoy. Soc. London, vol. clxiv. 1674, pp. 757-782, 4 plates. 



II Balfour, " The Anatomy and Development of Peripatvs eapensis,^^ 

 Quart. Jomn. Micr. Sci. vol. xxiii., 1883, 8 plates. 



^ Kennel, " Entwicldungsgeschichte von Peripatus" Arbeiten aus 

 dem zool.-zoot. Inst, in Wiirzburg, Bd. 7, 1885, pp. 95-200, Taf. v.-xi., 

 Bd. 8, 1888, pp. 1-93, Taf. i.-vi. 



** Sedgwick, " The Development oi Po'ipatus capensis,^ Quart. Journ. 

 Micr. Sci. vol. xxv. 1885, pp. 449-468, 2 plates, vol. xxvi. pp. 175-211, 

 3 plates, vol. xxvii. pp. 407-550, 4 plates ; " On the Fertilized Ovum of 

 and the Formation of the Layers in Peripatus" Proc. Koy. Soc. Lond., 

 vol. xxxix., 1885, pp. 239-244. 



ft Gaflron, "Beitragezur Anatomie imd Histologie von Peripatus,^' 

 Zool. Beitr. Schneid. 1 Bd., 1883-1885, pp. 33-60 and 145-165, 9 plates. 



XX Ryder, " The Structure, Affinities, and Species of ScolopendreUa" 

 Proc. Ac. Nat. Sci. Philadelphia, 1881, pp. 79-86. 



Ann. & Mag. N. Hist. Ser. 6. Vol. x. 31 



