86 NOTES AND OBSERVATIONS ON BOARD H.:M.S. RATTLESNAKE 



III. Upon Thalassicolla, a neiv Zoopliyte. 



In all the seas, whether extra-tropical or tropical, through which 

 the Rattlesnake sailed, I found floating at the surface the peculiar 

 gelatinous bodies which are the subject of the present communication. 

 They were the most constant of all the various products of the towing- 

 net, ^^■hich was rarely used without obtaining some of them, and which 

 sometimes, for days, would contain hardly anything else. 



The extreme simplicity of structure of these creatures was more 

 puzzling to me than any amount of complexity would have been. 

 The difficulty of perceiving their relations with those forms of animal 

 life with which I was familiar, gave me rather a distaste to the stud}- 

 of them, and, as I now perceive, has rendered my account of their 

 organization far less complete than I could wish it. 



However, these forms seem completely to have escaped the notice 

 of voyagers, and therefore I hope to do some service by directing the 

 attention of future investigators to them, and by endeavouring to show 

 what seem to me to be their relations in the scale of being. 



It may not be out of place at the same time to examine what are 

 the positive characters of those lowest classes of animal life of which 

 this is a member. 



The Thalassicolla}- is found in transparent, colourless, gelatinous 

 masses of very various form ; — elliptically-elongated, hour-glass- 

 shaped, contracted in several places, or spherical, varying in size from 

 an inch in length downwards ; showing no evidence of contractilitj' 

 nor any power of locomotion, but floating passively on the surface of 

 the water. 



Now of such bodies as these there were two very distinct kinds : 

 the one kind, consisting of all the oval or constricted, and man)- 

 spherical masses, is distinguished to the naked eye by possessing 

 many darker dots scattered about in its substance ; the smaller kind, 

 always spherical, has no dots, but presents a very dark blackish centre,, 

 the periphery being more or less clear. I will adopt the provisional 

 name of Th. punctata for the former kind, and that of Th. nucleata for 

 the latter, as a mere matter of convenience, and without prejudging 

 the question as to the existence of specific distinctions. 



Th. punctata. (PL XVI. [Pl^te ii] figs, i, 2, 3.) 



The mass consists of a thick gelatinous crust containing a large 

 cavity. The crust is structureless, but towards its inner surface minute 



^ Sixaaaa, the sea ; K(f.\Aa, jelly, glue. 



