126 COMPARATIVE ANATOMY. 



the sheath of the stock. The medusa buds arise without true 

 calyces, and assume the form of the genus fierce, causing this 

 form to resemble the ctenophorous ccelenteratates, as those 

 having true medusa buds resemble the discophorous. At 

 other times in -the same genus a hydraform bud escapes from 

 a simple calyx. It is not known which of these special gem- 

 mse produce the organs of generation. 



In Coryne, Hydra is a club-shape appendage to stock or 

 the medusa bud (Sarsia), develops eggs, as in Mteope, is asex- 

 ual, and develops other medusa buds from its proboscis, its 

 ovaries, or from the base of its tentacles (see Salpa, p. 128). 

 These remain attached for some time, but becoming sepa- 

 rated, develop organs of generation to bring forth planulse. 



In Hybocodon the medusa bud is developed directly from 

 the stock without calyx. It is peculiar in being asexual and 

 in possessing but one fully-developed tentacle. From the 

 base of this from ten to twelve other medusa buds arise to 

 remain attached. At this period the asexual bud becomes 

 free and swims off with its burden of special gemmae, each 

 of which evolves sexual organs to bring forth planulse. (E. C. 

 & A. Agassiz.) 



In Dicoryne male and female medusa buds arise from cap- 

 sules. They are of oblong form, but in place of disk present 

 two ciliated tentacles. (Allman.) 



The Discophoree, with some few exceptions, as in Campa- 

 nella, in which they develop, like the Ctenophorse, from eggs, 

 begin life as Hydra-like animals, the subsequent self-division 

 of which gives rise, by a singular process, to a number of 

 distinct jelly-fishes. (E. C. & A. Agassiz.) 



In Amelia, the impregnated egg is conveyed to a marginal 

 pouch from the ovarian chamber after a manner unknown. 

 It here develops into a hydraform larva (strobila, Scyphos-' 

 toma\ which subsequently undergoes transverse fissuration, 

 each segment (Ephyrd) assuming, during the process of divi- 

 sion, the form of the parent, afterward to develop sexual 

 organs and produce strobilse as before. 



Ctenophorse grow from eggs by a direct, continuous pro- 

 cess of development, without undergoing any striking meta- 

 morphosis. (E. C. & A. Agassiz.) 



