PROPAGATION OF MEDUSA. 



113 



Lizzia octopunctata. 



constructed organs has been recognized in many other species by various 

 observers. 



(292.) It was discovered by Sars*, that Fig. 52. 



certain forms of naked- eyed Medusae multiply 

 their species by means of gemmation, the buds 

 being produced either from the walls of the 

 peduncle or stomachal proboscis, or from the 

 surface of the ovaries. In both cases the 

 new individuals were not different from, but 

 similar to, their parents; and in one in- 

 stance, provision seemed to be already made 

 in the newly-formed offshoots for continuing 

 to propagate by the same mode other indivi- 

 duals similar to themselves. Prom a certain 

 part of the body roundish knobs grow forth, 

 which gradually assume the shape of a bell, 

 by opening themselves at the free end, and 

 soon present the form of young Acalephs, being merely attached to the 

 mother by means of a short peduncle, derived from the back of the 

 disk. These develope in themselves all essential organs whilst still 

 attached to the mother, like the buds of a plant, until at length, after 

 a certain time, they separate from the parent and swim about as inde- 

 pendent individuals. 



(293.) Professor Forbes, in his admirable monograph upon the British 

 Naked-eyed Medusae, not only confirms the above important observa- 

 tion of the Norwegian naturalist, but describes four different modes of 

 gemmiparous reproduction as occurring in that group of the Acalephae. 

 1st, gemmation from the ovaries, as noticed by Sars in Thaumantias 

 multicirrata ; 2nd, a mode of gemmation from the pedunculated sto- 

 mach, which he calls subsymmetrical, because in this case four gemmae 

 are symmetrically arranged round the peduncle, one of which is con- 

 stantly in a more advanced condition of development than the other 

 three ; 3rd, gemmation irregularly from the walls of a tubular pro- 

 boscis in which there is no order of development with respect to 

 position, individuals springing indifferently from various parts of the 

 peduncle (fig. 52) ; and a fourth mode, which is very remarkable, in 

 a new British species named Sarsia prolifera, in which 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 advancement, from embryo wart-like sproutings to 

 miniature Medusae, simulating, in their essential characters, the parent 

 animal. 



(294.) We have already seen, at the close of the last chapter, that 



* Fauna Norvegica. 



1 



