MOLLUSCOlDA. . 315 



conformation differs much from that which is proper to the connected 

 Salpa; so different, indeed, that it might belong to another type. 

 Chamisso, Krohn, and Milne Edwards have ascertained that the 

 Biphora is viviparous, and that each species is propogated hy alternate 



Fig. 127. Phosphorescent chain of Salpas on the surface of the sea. 



generation, the young creature being unlike its immediate parent. 

 One of these generations is represented by the solitary individuals, the 

 other by an aggregation of individuals. Each solitary Biphora en- 

 genders a new group a chain ; each constituted member of the chain 

 CD genders a solitary Salpa. 



Thus a Salpa is not organized like its mother or daughter, but 

 rather like its sister, its grandmother, or granddaughter another 

 example of alternate generation, which has already been discussed in 

 treating of zoophytes. 



Those marine creatures which pass their lives in a forced community 

 animals which eat, sleep, or rest always in company who abandon 

 themselves together to the soft caresses of the waves, these colonies, 

 or, rather, republics of animals, leading constantly the same mono- 

 tonous existence, reveal to us very strange things : an identical com- 

 munity of sentiments in a crowd of beings riveted by the same 

 chain a chain at once physical, intellectual, and moral ! 



