40 



THE AMERICAN NATURALIST 



they remain longer, for, according to Mobins, the young 

 of the European oyster leaves the parent at a size of .15 

 to .18 mm. (Horst gives .16 mm.; Huxley Hso inch). I 

 have taken larvae of 0. lurida in plankton ( identified by 

 comparison with those from a parent, and also by the 

 structure, shape and size) of a length of .165 mm. as well 

 as different larger sizes. They still had a straight4ringe 

 line of half the length of the shell— unlike the 0. virginica 

 which at this size is already passing into the umbo-stage 

 and with a much shorter hinge-line. The larva? of 0. 

 lurida are not pink or brown but have five or six dark 

 blotches in the region of the liver and in the velum, in 

 contrast to the general light shade of the rest of the 

 animal. 



