GENERA. 17 



gemmation, and a very remarkable and quite novel one, I have discovered in another form of 

 Sarsia, taken abundantly in 1836 on the coast of Cornwall, and named by me Sarsia proUfera. 

 In this extraordinary animal the buds are produced at the bases or tubercles of the four marginal 

 tentacles, and hang from them in bunches, like grapes. The degree of development is not 

 equal in all four bunches, and in each case buds are seen in very various stages of develop- 

 ment, from embryo wart-like sproutings to miniature Medusae, simulating in their essential 

 characters the parent animal. [See figures and description of Sarsia prolifera in the synopsis 

 of the species.] 



I look upon this last discovery as very important in its bearing on the history of this 

 phenomenon of gemmation among these creatures, seeing that in the case under consideration the 

 seat of reproduction is not in the peduncle, where in Sarsia the true ovaries might be supposed 

 to be seated, since they are not manifest elsewhere, but in a portion of the animal quite apart. 

 It would appear, indeed, that gemmation can occur anyw^here in the course of the granular 

 motor tissue, or from the true ovaries, but not from other than the motor, and especially 

 reproductive, tissues. The power of the motor tissue to produce germs occurs also in other 

 orders of Medusae : for I have seen the same phenomenon in the Beroe. When treating of 

 the phosphorescence of the naked-eyed Medusae, we have seen that that phenomenon was 

 exhibited either by the ovaries, or centre (peduncle) or bases of the tentacles and rim ; all, as 

 I have just proved, seats of reproductive power. This goes far to connect that phenomenon 

 with the generative functions. 



The development of the ovum in the naked-eyed Medusae has still to be observed. Not 

 until the phenomena attending it have been made known, can we hope to ascertain the history 

 of the metamorphoses which they possibly, indeed most probably, undergo before arriving at 

 the state in which we usually find them. 



The preceding outline of the structure and physiology of the naked-eyed Medusae, so far 

 as known, will enable the reader to understand the detailed account of our British genera and 

 species, which I shall now proceed to give, reserving remarks on their zoological afl&nities as 

 a group, for a review of the subject at the conclusion of the synopsis, when we shall have 

 the necessary evidence before us. 



There are forty-three species of Gymnopthalmatous Pulmograda known to the author 

 as inhabiting the British seas. The greater number of these are undescribed forms. They 

 may all be arranged under eighteen Genera, grouped together as in the following table : 



I. Vessels branched. (Willsiad^.) 



1 . Willsia. 



II. Vessels simple ; ovaries convoluted, and lining the pedunculated stomach. 



(OCEANID^.) 



2. Turris. 



3. Saphenia. 



4. Oceania. 



III. Vessels simple, eight or more ; ovaries linear, in the course of the vessels on the 



sub-umbrella. (^Equoread^.) 



5. Stomobrachium. 



6. Polyxenia. 



