264 



INVEETEBEATA 



CHAP. 



the surface. We find also an embryonic area from which nuclei are 

 budded off into the interior, but this area is very short indeed 



coe 



coe 



v.m- 



v.nc. 



Fi. 208. Transverse sections through three einliryos of Phyllodromia gennanica at three 

 stages of development in order to show the development of the coelomic sacs. The 

 fat liody, and the generative organs. (After Heymons.) 



A, the youngest stage. B, intermediate stage. C, oldest stage, after the completion of the dorsal 

 surface, coe, coelomic sac ; up, epineural sinus ; f.li, fat body ; fil.p, terminal filament plate of the genital 

 organ ; </, germ cells ; gen, accumulation of germ colls forming the genital organ ; H, heart ; stig, stigma 

 of trachea ; v.m, ventral longitudinal nerve ; v.n.c, ventral nerve cord. 



compared to the length of the egg. The cells which are budded 

 inwards give rise to the yolk cells, and also to those cells which, at a 



fll 



p * ^ ~' 



T y ; >7-' ,.'' '* ' -'is .-: 7 -\ 



Fie. 209. The rudiment of the female genital organs of /'/ii/f/in/nniiifi 

 reconstructed from sagittal sections. (After Heymons.) 



Jil, terminal lilament ; ,fil.]i, plate uniting u]>per ends nf tin- terminal filaments ; germ, germ cells ; 



iir/l, rudiment nt oviduct. 



comparatively late period in development, assemble on the surface 

 of the yolk and constitute the endoderm. 



The mesodermic bands arise later by proliferation from the 



