Royal Physical Society. 65 



mens ; but he has seen numerous transparent gemmules in the 

 water in which Cydippes were kept. Agassiz states, that 

 although he had kept Cydippe alive for months during the 

 spring, he had never seen in any of them anything like ovaries 

 or spermaries. He also writes that although he has watched 

 Bolina through six successive months, from December to June, 

 he had never succeeded in discovering the sexual system even 

 in its most rudimentary state, and that of their embryonic 

 development nothing is known ; and yet these Acalephs fre- 

 quently swarm in the seas both of Europe and America. The 

 reproductive processes in several species of the pulmograde 

 Acalephae have been investigated with great success by Sars, 

 Dalyell, John Reid, Steenstrup, and others. The Steganop- 

 thalmata (of which Aurelia aurita, the common "jelly-fish" 

 of the Firth of Forth, is an example) at certain seasons of the 

 year pour forth from their ovaries multitudes of germs, which 

 affix themselves to shells and other bodies, and became many- 

 tentacled hydraform polypes. These polypes, after multiply- 

 ing by gemmation for many months, perhaps years, begin to 

 resolve themselves by transverse fissure into minute medusae, 

 which undergo many changes before they arrive at their adult 

 form and size. The Gymnopthalmata (those tiny naked-eyed 

 medusae which, visible to the naturalist alone, swarm in im- 

 mense multitudes around our coasts) emit ova which are 

 developed into polypes of various form, either single, as Cory- 

 morpha, or united together by creeping fibres or stems, in 

 colonies of plant-like form, as Clava, Coryne, Tubularia, Cam- 

 panularia. In spring, these zoophytes put forth buds, either 

 from their polyparies or from the polypes themselves. The 

 buds rapidly enlarge, and are developed into bell-shaped me- 

 dusae, which, after remaining attached for a short time to the 

 parent stem, become detached, and flap themselves away in the 

 surrounding water. The reproduction of these plant-like ani- 

 mals bears, indeed, a remarkable resemblance to that of the 

 true plant. The flower of the plant produces a seed, the me- 

 dusa of the zoophyte an ovum ; the seed grows into a stem and 

 leaves, the ovum into a stem-like polypary and polypes ; the 

 plant multiplies itself by suckers and bulbils, the polypary by 



