CRANGON VULGARIS. 145 



mesoderm and endoderm cells have no such appearance in 

 Craiigon. 



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

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

 Ihe 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 enibryo 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 (amnion and serosa) of hexapods, nor have they 

 any connection with the dorsal organ (micropjlar 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 bat little to 

 Support it. 



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

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

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

 been formed between the antennulse and the thoracico-ab- 

 dominal area. The antennulse 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, af. 



