FORMATION OF THE YOUNG ANIMAL 



67 



the Chilopoda have the full number of legs in some cases ; in 

 others only a small number of legs, but yet more than the three 

 pairs of legs of the Chilognatha, and fully developed instead of 

 stump-like. The eyes are usually developed late in the life of 

 the young animal. The bursting of the egg-shell is assisted in 

 some Myriapods by a special kind of spike on the back part of 

 the head. 



The Fig. 40 shows a young Chilognath which has just burst 

 the shell and come into the outer world. 

 It is still surrounded with a membrane 

 which has been formed by its skin or 

 epiblast within the egg. One eye-spot has 

 been formed. 



Fig. 41 shows a longitudinal section 

 through the young Chilognath shown in 

 Fig. 40, and the next (Fig. 42) a transverse 

 section through the same. In comparing 

 the two Figs. 41 and 42 it must be remembered that they are 



Fig. 40. Young Jnlus ter- 

 restris just hatched. 



snjf.ce 



mem.ejc: 



nxfang. 



Tig. 41. Longitudinal section through late stage : Siip.oe.ffl, First appearance of brain ; 

 st, mouth ; pr, anus ; mesen, gut ; n, nerve cord ; n.ffanff, nerve ganglion ; mem.ex, 

 membrane surrounding the animal ; v.f, ventral flexure ; mes, mesoblast cells. 

 (Heathcote, Post. Emb. Dev. of Julus te/restris.) 



sections in different planes through the animal shown in Fig. 40, 

 and therefore they only show a small portion, a thin slice, of the 



organs. 



