SARSIA. 69 



boscis, hanging from the under surface of the disk to a consider 

 able distance below its margin. The four tentacles are of an 

 immense length when compared to the size of the animal. As a 

 general thing, the tentacles are less numerous in the Tubularian 

 Medusa3 than in those arising from other Hydroids ; they want 

 also the singular limestone concretions found at the base of the 

 tentacles in the Campanularian Medu 

 sae. In Fig. 91 we have one of the 

 Tubularian Medusas (Turrit vesicaria 

 A. Ag.) which has a rather larger 

 number of tentacles than is usual 

 among these Jelly-fishes. We never 

 find the tentacles multiplying almost 

 indefinitely in them, as in Zygodac- 

 tyla and Eucope. The little Jelly-fish 

 described above is known as Sarsia, 

 while its Hydroid is called Coryne. 

 These names having been given to 

 the separate phases of its existence 

 before their connection was understood, 

 and when they were supposed to rep 

 resent two distinct animals. They are 

 especially interesting with reference 

 to the history of Hydroids in general, 

 because they were among the first of these animals in whom 

 the true relation between the different phases of their exist 

 ence was discovered. Lesson named the Sarsia after the great 

 Norwegian naturalist, Sars, to whom we owe so large a part of 

 what is at present known respecting this curious subject of alter 

 nate generations. 



JBougainvillia. (BougawviUia superciliaris AG.) 



The Bougainvillia (Fig. 92), is one of our most common 

 Jelly-fishes, frequenting our wharves as well as our sea-shore 

 during the spring. The tentacles are arranged in four bunches 



Fig. 91. Turris vesicaria ; natural size. 



