CRANGOX VDLGAEIS. 145 



mesoderm and endoderin cells have no such appearance in 

 Crangon. 



It is at this stage that I have first distinctly seen the 

 first embryonic cuticle, though I have seen traces of it in 

 the stage A. It is a delicate, cuticular pellicle, secreted 

 by all the cells of the blastoderm and forms a second en- 

 velope inside the chorion. Its fate I have not traced. 

 What these blastodermic cuticula mean from a phyloge- 

 netic standpoint I am not ready to say. They occur in 

 various arthropods, having been described in many Crus- 

 tacea and some Arachnids as well as in Limulus (Kings- 

 ley, '85). In Atax, Limulus and Apus they form a 

 protective envelope for the embryo after the splitting of 

 the chorion, and in such cases Claparede's term deutova 

 may be applied to them. In other cases they seem to 

 play no part in the subsequent history of the animal. 

 They clearly have no connection with the protective en- 

 velopes (amniou and serosa) of hexapods, nor have they 

 any connection with the dorsal organ (micropylar appa- 

 ratus) of the Edriophthalma. Kennel ('84) sees in them 

 a remnant of the trochosphere of the annelid ancestor of 

 the arthropods, a view which seems to have but little to 

 support it. 



In stage (7 (figs. 12 and 13) the optic lobes are more elon- 

 gate, the upper lip (I) has developed, covering the mouth, 

 while a second pair of appendages (//), the antenna?, have 

 been formed between the antennulse and the thoracico-ab- 

 dominal area. The antennulee and the mouth begin to show 

 a change in their relative positions, for while in the last 

 figure the base of this appendage was distinctly postoral, 

 it has now moved forward so that the mouth is opposite 

 the middle of the base. The abdomen is also farther de- 

 veloped by the inpushing of the pouch already described, 

 the extent of which is best shown by the side view, fig. 

 12, of. 



