192 



•with specimens of the Echinus chlorocentrotus Brandt, which Mr. Agas- 

 siz had collected himself at Vancouver's Island, in the Gulf of Georgia, 

 W. T., and was satisfied that the species described by Brandt could 

 not be distinguished from the Toxopneustes drobachiensis Ag. He had 

 also examined specimens of the same species from Hudson's Bay, col- 

 lected by Mr. Drexler, and from New Jersey, which belonged to the 

 collection of the Smithsonian Institute. 



This species of Echinus is, then, without doubt, found on both sides 

 of the Old and New Worlds, and along the whole arctic coast of Asia 

 and North America, descending on the Asiatic side as far south as the 

 southern extremity of Kamtschatka ; on the Pacific side of North 

 America as far south as the Gulf of Georgia and the Straits of Fuca ; 

 while on the Atlantic side it extends as far south as the coast of New 

 Jersey in America, and the Shetland Islands and the southern extrem- 

 ity of Norway and Sweden in Europe. 



But, while admitting this extraordinary range of distribution, Mr. 

 Agassiz remarked that, although he had not been able to perceive any 

 difference in the adults, yet he was not prepared to say that future 

 investigations would not point out permanent differences in the young 

 of specimens from these remote localities. In support of this he 

 brought up the case of the three species of Coryne, one found on the 

 west coast of North America, the other on the eastern coast, and the 

 species from England, the adult free Meduste of which it was almost im- 

 possible to distinguish, while file Hydras were so distinct that they would 

 not be confounded by the most casual observer. He also mentioned the 

 case of Sarsia and Syndiction, the free Meduste of which could hardly be 

 distinguished ; but yet in their Hydra state, and during the earlier pe- 

 riods of their Medusa state, they were as different as possible in their 

 appearance — in fact belonged to two very well-defined genera. He 

 also made allusion to a paper of Rev. Mr. Hincks in one of the last 

 numbers of the Annals and Magazine of Nat. Hist., who had from simi- 

 lar facts drawn the conclusion that Hydrse belonging to different genera 

 could produce Meduste belonging to one species. He thought that 

 this conclusion was hardly logical, but simply implied our inability to 

 distinguish adult Meduste belonging to closely-allied genera in the pres- 

 ent state of our knowledge. Mr. Agassiz mentioned also the case of 

 many of the free Medusae of our Campanularians, which he had at 

 first mistaken for the same species, but which, upon raising from the 

 Hydra, and tracing in all their stages, he could now easily distinguish. 



The following are the different localities from which there are spe- 

 cimens of Toxopneustes drobachiensis Ag. in the Museum of Com- 

 parative Zoology at Cambridge : — 



