66 



MYRIAPODA 



into the outer world. The various processes may be understood 

 by reference to the Figs. 36, 37, 38, 39, which are ^succes- 

 sive stages in the development of a Chilognath. Figs. 37, 38, 

 are thin slices through the shorter diameter of the egg, which, as 





i_ 



<Li-_J )"■ -^ I-"—' '--^ 1-1 LJ 





Fig. 38. — Transverse section 

 through next stage : vik, 

 keel-like mass of cells from 

 which the mesoblast is pro- 

 duceil ; ec, ej^ihlast. (From 

 Heathcote, Post. Emb. Dev. 

 ^- of Jidus terrestris ; Phil. 

 Trans, vol. 179, 1888, B.) 





before mentioned, is an oval in shape. Fig. 39 is a section 

 through the longer diameter of an egg in a more advanced stage 

 of development, in fact just about to burst the shell. The body 

 of the future animal is marked by constrictions, the future 

 segments. Some of the organs are already formed, as the brain 



Seq.2. 

 tnes. '^ \ 



Cepfi Seg. 



Fig. 39. — Longitu- 

 dinal section 

 through later stage: 

 Segs. 2, 3, etc. , seg- 

 ments ; Ce^h.Seg, 

 head ; mes, meso- 

 blast ; e5i,hypoblast ; 

 sijfuture mouth ;^/-, 

 future anus ; inesen, 

 gut ; vie7/i.ex, as in 

 Fig. 41. (From 

 Heathcote, Post. 

 Emb. Dev. of Jidus 

 terrestris. ) 



and the digestive tube, the openings of which will form the 

 mouth (st) and the anus (pr). 



Myriapods are hatched at different stages of development. 

 The Chilognatha have only three appendages, which are so 

 little developed that they are only small shapeless stumps, while 



