74 WHEELER. [Vol. V 1 1 1 . 



the ventral surface of the ^gg, but whether or not it exhibits 

 any traces of blastokinesis my limited material will not enable 

 me to decide, and Graber ('77), Bruce ('86), and Viallanes 

 ('90^ '90^'), have contributed no observations bearing on this 

 point. It is clear, nevertheless, that in its development, Mantis 

 resembles Dlatta more closely than either of these forms re- 

 semble the Saltatoria. This merely confirms the view which 

 has long been held respecting the affinities of the Blattidae 

 and Mantidae. From the structural similarity of the Phas- 

 midae and Mantidae we may venture to infer a similarity of 

 embryonic development. 



It thus appears that the Orthoptera are clearly separable 

 into two groups — the Saltatoria on the one hand and the 

 Gressoria and Cursoria on the other. The Saltatoria are 

 decidedly blastokinetic whereas the non-saltatory forms re- 

 tain only faint reminiscences of blastokinesis {Blatta). I 

 am inclined to believe that primitive embryological features 

 have been preserved more faithfully in the Saltatoria than 

 in other Orthoptera. That the habits of oviposition are more 

 primitive in this group is shown by Brongniart's discovery of a 

 fossil Blattid provided with an ovipositor ('89). Moreover, several 

 features in the development of the Saltatoria show great con- 

 servatism, e.g. the retention of the indusium in the Locust- 

 idae, the order in which the metameres arise, and the myriopod- 

 like habitus of the Xiphidium embryo in Stage D. 



Not only does a study of the Saltatoria throw light on the 

 development of other Orthoptera, but it brings the order into 

 closer union with the Odonata and Rhynchota. The blasto- 

 kinesis of the Gryllidae agrees closely with that of the Hydro- 

 corisa among the Hemiptera — e.g. Corixa, as described by 

 Metschnikoff ('66). Ranatra and Zaitha will bear even a closer 

 comparison with the Gryllidae. In the much elongated ^gg of 

 the former, which has the cephalic pole marked by the pair of 

 diverging pneumatic threads, the germ-band arises as usual on 

 the ventral surface with its head directed upwards. As the 

 envelopes develop it passes around the lower pole and finally 

 assumes an inverted position on the dorsal surface. During 

 katatrepsis it returns over the same path. The inclusion ob- 



