J. D. Tothill — The Ancestry of Insects. 



375 



abdominal segments, namely, 11, is retained, the tritocerebral 

 appendage shows as a rudiment in the young embryo (Hey- 

 mons, '97), and there are 11 pairs of spiracles whereas in the 

 winged insects these are reduced to ten. In Anurida mari- 

 time!, (fig. 1, C and D) studied especially by Claypole ('98) the 

 mouthparts show considerable reduction as also do the eyes ; of 

 particular interest is the reduction of abdominal segments ; 



this singular animal shows 



also according to the same author 



Fig. 1. 



Fig. 1. 



A. Lepisma saccharina, young embryo. (After Heymons.) 



B. " " mature embryo. (After Heymons.) 



C. Anurida maritima. Very young embryo showing the tritocerebral 



appendage tc. (After Wheeler.) 



D. Anurida maritima, adult showing collophore, reduced mouth parts, 



and reduction of abdominal segments. (After Claypole.) 



E. Sminthurus. Young embryo showing reduction of abdominal seg- 



ments. (After Lemoine.) 



F. Anurophorus. Embryo showing reduction of abdominal segments. 



(After Lemoine.) 



no traces whatever of a tracheal system ; on the other hand the 

 first pair of abdominal appendages is preserved as the collo- 

 phore (Claypole, Wheeler) and the same authors agree that 

 the tritocerebral appendage is preserved (fig. 1, C). In Smin- 

 thurus (fig. 1, E) and Anurophorus (fig. 1, F) there is specializa- 

 tion by reduction of mouthparts, eyes and abdominal segments ; 

 on the other hand several pairs of abdominal appendages are 

 preserved even in the adult condition. 



