Royal Physical Society. 67 



Agassiz, after careful examination of Cydippe and Bolina, 

 and comparison of their anatomy with that of Sarsia mirabilis, 

 one of the Gymnopthalmata, considers it highly probable that 

 the former are, like Sarsia, the product by gemmation of hydroid 

 polypes ; and he particularly directs the attention of future 

 investigators to the determination of this question. On this 

 point it has been my good fortune to make the following ob- 

 servations : I found in the water of Morecambe Bay, one day 

 in June 1853, swarms of the Cydippe pomiformis. Every lit- 

 tle creek and channel in the sand-banks was full of them, 

 where a day or two before and afterwards not one was to be 

 seen. On examining one of these animals confined in a jar of 

 sea-water, I observed a great number of transparent vesicles 

 in the lateral water-vascular canals. Some of the vesicles 

 were floating freely in the circulating fluid, but the greater 

 number were attached in pairs to the inner surface of the 

 muscular bands, a pair between every two of the ciliary pad- 

 dles, fig. 2. The constant motion of the pad- 

 dles rendered it difficult to ascertain the true 

 nature of these vesicles ; but the next day a 

 considerable number were floating freely in the 

 jar, and were placed under the microscope. 

 They consisted of a transparent and highly re- 

 fractive vitellus, containing a germinal vesicle 

 and germinal spot, and surrounded at a consi- 

 derable distance by a thin envelope or shell. Several of the 

 ova were placed in a small trough of sea-water, and carefully 

 watched for some days, but no further development occurred 

 in them. In the meantime the water containing the parent 

 Cydippe was examined every day with a single lens, and after 

 a few days minute bodies about the size of a rape-seed were 

 detected swimming amongst the eggs. These proved to be the 

 hatched young of Cydippe. The rest of the ova were found 

 in all stages of the advance towards full development. In illus- 



by a mass of well-formed spermatozoa; the two coats were united at the mouth, 

 which was surrounded by a ring of large thread cells. The peduncle was, in 

 fact, but little advanced from the simple sperm-sac I have described above. All 

 the medusae on the polypary were males. May we not infer from this the pro- 

 bability of the medusa-bearing zoophytes being also dioecious ? 



