EMBRTOLOQT OF 0NI8GUS. 



307 



shaped, widest behind. The intestine is on its anterior half 

 broader than the stomach, suddenly contracting behind. 



Fig. 256 — Diesection of -y(?ro;i5 to stow the nervous system. — Dissected and drawn 

 by J. S. Kingsley. 



There is no coecal enlaigement, and no "urinary" tubes. 

 The sexes are distinct. The young are hatched in the form 

 of the adult, there being no metamorphosis. 



The development of the i^ill-bug, Oniscus mm'arius is 

 probably typical of that of most Tetradecapods and Deca- 



Fig. 257.— Transverse section of SeroOs. t, t, tergum ; s, s. sternnm ; em, epime- 

 rnm ; es, episternum, at insertion of the Jegs.— Prepared and drawn by J. S. Kings- 

 ley, 



pods (Bobi-etzky). The first change after fertilization is the 

 origin of the formative or primitive blastodermic cells at oae 



