CAMPANULARIA. 217 



if I be right, a correspondence appears between their developemeut and 

 that of the Medusa ocilia. But I should desire an opportunity of repeat- 

 ing this observation. Considerable exertion seems requisite for liberation, 

 and many perish in partial protrusion. All having quitted the vesicle, an 

 opaque columnar substance, with an enlarged summit, remains. 



The life of these creatures is transient; they disappear insensibly, 

 or they fall to the bottom of their vessel, where they die. The longest 

 period I have been able to follow them was nine days, when they still rose 

 a little amidst the water. 



During March and some subsequent months of summer, numerous co- 

 lonies of the T'mtinnahulum have been produced in different years from such 

 vesicles as above described. No other animals have ever issued from them. 



The figures given by Ellis, Plate xxxviii. fig. 3. B. and by a later 

 author, Mr Lister, in the Philosophical Transactions, Vol. cxxiv. PI. x. 

 as of young hydrse escaping from the vesicles of the Sertidaria dichotoma, 

 are quite unintelligible by me. No doubt it is possible, however impro- 

 bable, that the ovum in the vesicle of a Sertularia may relax as a planula ; 

 that a spine may originate from the planula if retained long enough, and 

 then a hydra. But all this is adverse to the ordinary course of nature. 



If the accounts of the two authors now named could be reconciled 

 to any facts that have occurred to me, I should conclude that it is the 

 Tintinnabidum they have seen escaping from the vesicle of the Sertularia 

 dichotoma. 



A series of accurate observations on multiplied specimens has still 

 to determine the real distinctions of the Campanularia dichotoma, the 

 C. genicidata and gelatinosa. 



Plate XLI. Fig. 1. Sertularia dichotoina. 



2. Hydra and bell, front. 



3. Hydra and bell, profile. 



4. Portion of a branch with a hydra and vesicles, showing 



their relative proportions. 



5. Portion of a branch with immature hydrse still in their cells, 



and a hydra in retreat, a. 

 VOL. I. 2 E 



