A NEW rOLYZOON. 337 



showed it tobe aPolyzoon, much resembling the Alcyonidium 

 hirsutum. It was single, however ; and on other parts of 

 the glass were eight other specimens, all solitary. This was 

 in itself noticeable, because, as the name Polyzoon imports, 

 these animals live in colonies. Under the microscope, a new 

 fact presented itself : the animal was enclosed in an oblong 

 bivalve-shell, which seemed permanently open on one side, 

 and open at the summit to give passage to the crown of ten- 

 tacles. Imagine a shell like that of a mussel gaping open, within 

 which is a quinine bottle, the broad neck protruding, and you 

 will form a tolerable idea of the general aspect of this animal 

 when the tentacles are withdrawn. I believe this to be a 

 new genus, and also to have an interest beyond novelty, 

 because furnishing another decisive argument in favour of 

 the molluscan nature of the Polyzoa — a point still disputed 

 among naturalists.* The existence of a bivalve-shell is very 

 important ; and I took pains to convince myself that it was 

 really a shell, and not a membranous envelope having the 

 aspect of a shell : submitting the animal to decomposition, I 

 found the shell remain behind intact. 



Apropos of Molluscs : their powers of endurance are very 

 remarkable. Having noticed that they live out of their 

 native element, the water, for a considerable time, being 

 often left bare on the rocks by receding tides, I thought of 

 testing their powers in this way. Accordingly, a Cockle was 

 placed on my work-table, out of all reach of damp, in a room 



* The recent publication, by tlie Ray Society, of Professor Ai.lji.vn's 

 monograpli on Freshwater Pobjzoa, must for ever settle this dispute. 



2 F 



