DEVELOPMENT OF E. TRIACANTHA 



277 



Post-Larval Stages 



Sixty-seven specimens of post-larval stages, all taken in one net haul in late February, 

 were examined to discover at what size the tergal collar of the first somite of the ab- 

 domen, which serves to distinguish certain of the Furcilia stages from those of E.frigida, 

 is lost ; and at what sizes two structures characteristic of the adult, the broadly rounded 

 antennular lappet and the spine of the third abdominal somite, appear. It was found 

 that the tergal collar was absent from all and that the spine appeared before the lappet. 

 An analysis of the specimens is shown below in lettered groups and the lengths of those 

 of each group in Table V. Groups A, B and C were measured with greater accuracy 

 than the larger individuals of groups D and E. 



A. Without the beginnings of the abdominal spine ... ... ... ... 18 specimens. 



B. With the beginnings of an abdominal spine : a small projection only ... 11 specimens. 



C. With a well-developed abdominal spine but with no lappet, or with the small 



beginnings of a lappet 13 specimens. 



D. With lappet less than, or about, half-formed 16 specimens. 



E. With lappet of shape and proportions of the adult 9 specimens. 



Table V. Showing lengths {in mm.) and numbers {in brackets) of post-larval E. vallentini, 

 arranged according to the development of the abdominal spine and the antennular lappet 



A 



B 



7-5 (I) 



9-2 



C 



9-0 (i) 



D 



12 (4) 



13 (5) 



H (5) 



15 (2) 



