432 M. N. Cholodkowsky on the 



should do better to wait a little before we homologize the 

 mouth-parts of Mjriapods, Arachnids, and Insects, not to 

 mention Crustacea. For our knowledge of the development 

 of Myriapods is as yet altogether too scanty, and even the 

 embryology of Insects and Spiders needs completion. Under 

 such conditions it would be far too daring to attempt an homo- 

 logization of the mouth-parts of Arthropods at present. One 

 thing I believe is certain, namely that the antennse of Insects, 

 and in all probability of the Tracheata in general, are true 

 homologues of the appendages of the trunk, and therefore do 

 not correspond to the pre-oral antennge of Peripatus. It is 

 also hardly open to doubt that the group ACERATA (Poecilo- 

 poda and Arachnida) established by Kingsley does not corre- 

 spond with its name, for there exists no reason at all for 

 considering the cheliceree to be not homologous with the 

 Insectan antennae. There is also no justification for Lang's 

 proposed division of the Tracheata into Antennata (Myria- 

 poda and Hexapoda) and CheliCERATA (Arachnida), since 

 the Arachnida, on the basis of the development of the cephalic 

 extremities, are not separable from the Antennata. 



Among other appendages of the germinal streak of Insects 

 those belonging to the abdomen are also very interesting, and 

 I will now discuss them somewhat more in detail. As we 

 have seen (Chapter III.) the embryo of Blatta germanica 

 possesses eleven pairs of abdominal appendages, which, 

 according to all appearance, are completely homologous with 

 the thoracic legs. It is here my intention to consider those 

 abdominal appendages which persist for a longer time in the 

 post-embvyonic development, such as the pro-legs of cater- 

 pillars and Tenthredinid larva3, the abdominal appendages of 

 the Thysanura, &c. 



With reference to the abdominal appendages of Campodea 

 and 3IacJnIis, the prevalent view for a long time was that 

 they are homologous with the true legs. Only a few investi- 

 gators, such as Burmeister *, declared against this theory. 

 Considerable doubt has recently arisen as to the significance 

 of these appendages as rudiments of legs ; for certain authors 

 believe that they correspond not to the legs, but to the coxal 

 appendages, which are also present upon the thoracic legs. 

 If this view, which is based exclusively upon anatomical 

 facts, is correct, abdominal legs provided with coxal appen- 

 dages must nevertheless exist in embryonic life in the case of 

 Machilis and Camijodea also and be able to subsequently 

 disappear, leaving only their coxal appendages behind. (Jon- 



* riurmcistin', ' ITniulbnch der Entnniolngie," Bd. 2, 18'58, p. 454. 



