130 



2. Relative length of preoral part of larva. 

 This part is usually less or almost equal 

 in length to the postoral part. Exceptions 

 are the bipinnariae of the family Luidiidae 

 in which, as a result of growth of the 

 medioventral and mediodorsal processes, 

 the preoral part is longer than the postoral. 



3. Relative length and movability of paired 

 processes of bipinnaria. In bipinnariae of 

 the families Astropectinidae, 

 Gymnasteriidae, and Asterinidae, the pro- 

 cesses are relatively short and less mov- 

 able. In bipinnariae of the family 

 Asteriidae and some species of the family 

 Luidiidae, they are longer and capable of 

 greater movement. 



4. Relative length and movability of 

 brachiolar arms. In brachiolariae of the 

 families Gymnasteriidae, Asterinidae, and 

 Acanthasteridae, the brachiolar arms are Figure 87: Brachioiaria of Asterias 

 relatively short and less movable than in ''^bens (Gemmili, 1914) 

 brachiolariae of the family Asteriidae. 



5. Degree of development of unpaired brachiolar arms. In brachiolariae of 

 the family Asteriidae, the middle brachiolar arm is similar in structure to 

 the lateral ones. Two short lateral rows of small papillae occur on the 

 ventral surface of the middle brachiolar arm near its base. In brachiolariae 

 of the families Poraniidae, Asterinidae, Acanthasteridae, and some oth- 

 ers, the middle brachiolar arm is a relatively less modified medioventral 

 process, with two long rows of papillae on the ventral surface. 



6. Color of larva and of its processes. 



Identification of larvae before the late bipinnaria stage is difficult. 



Key to Larvae Based on Late Bipinnaria Stage 



In Peter the Great Bay sea stars belonging to five families of three orders 

 have been found. In Henhcia sp. (family Echinasteridae) and Solester sp. 

 (family Solasteridae), development proceeds with lecithotrophic larva, and 

 the bipinnaria stage is absent; only a modified nonfeeding brachioiaria stage 

 occurs. 



