450 On the Morpliology and Phylogeny of Insects. 



Haase, Nassonow '^, Grassi f, Oudemans \, and others upon 

 the morphology of the lower Insects and Myrlapods. The 

 fact, which was brought forward by myself for Blatta ger- 

 manica and confirmed by Graber, of the remarkable division 

 of the cavity of each somite into three sections, one of which 

 is, in my opinion, homologous with the segmental funnel of 

 Peripatus^ seems to decide the question still more definitely in 

 favour of the derivation of the Insects from homo- and poly- 

 pod and, probably, ScoIopend7'ella-\ike ancestors. Even 

 Graber, who, as I think, ascribes too great importance to the 

 saccate shape of the first abdominal appendages, nevertheless 

 considers it probable that the ancestors of the Insects were 

 Myriapod-like, and admits that this supposition appears 

 h priori to have most to be said in its favour. If, however, 

 we weigh the great differences between the Crustacea on the 

 one hand and the rest of the Arthropoda on the other, a close 

 relationship between Insects and Crustaceans appears simply 

 impossible. The Nauplius-form. of larva, an exclusively 

 Crustacean possession, the remarkable resemblance in embry- 

 onic development between Insects and Peripatus, and the con- 

 stitution of the respiratory and excretory organs, are facts which 

 all compel us to conclude that the Arthropod type is at least 

 diphyletic in origin. The Crustacea, indeed, are to be 

 derived from marine Annelids, which in the course of their 

 development passed through the Trochosphere stage (which 

 in the Crustacean development became transformed into that 

 of the Nauplius), while for the ancestors of the Tracheata we 

 must look to terrestrial or freshwater Annelids, more of the 

 Oligochgete type. The subtype Tracheata is at present 

 rejected by several zoologists, since the Arachnids are sepa- 

 rated from the rest of the air-breathing Arthropods and 

 approximated to the Poecilopods. I have above already 

 adduced the evidence against the establishment of the groups 

 Acerata (Kingsley) and Antennata (Lang), and here need 

 only add that the mode of development of the respiratory 

 organs of the Arachnids (Schimkewitsch §, Morin ||) tells, in 



* Nassonow, " Zur Morphologie der niederen Insekten," Naclir. der 

 Moskauer Ges. der Freunde der Natm-wissenschaft &c., Bd. 52, Lief 1, 

 1887 (in Eussian). 



t Grassi, " I prog-enitori dei Miriapodi e degli Insetti,'' Atti Accad. 

 Gioenia Sc. N. Catania, (3) vol. xix., 1886, 83 pp. 5 plates ; Bull. Soc. 

 Ent. Ital. 1886, pp. 173-180, tt. 7, 8 ; Atti Accad. Liucei, (4) vol. iv., 

 1888, pp. 543-606, 5_ plates. 



X Oudemans, ' IJeitrage zur Kenntuiss der Thysanura und Collembola,'' 

 Berlin, ^889. 



§ Scliimkewitscli, " Etude sur le developpement des araignt^es," Arch, 

 de Biologie, t. vi., 1885, pp. 615-584, pis. xviii.-xxiii. 



i| Morin, " Zur Entwicklungsgescbichte der Spinnen," Biol. Centralbl. 

 vi. Bd., 1887, pp. 658-663. 



