68 THE FISSIGEMMATION AND 



Scyphostoma. In a general way, it is like the Hydra in structure, 

 but when fully developed it has as many as twenty-four tenta- 

 cles at the broad end of the body, disposed 

 in a wreath at a short distance behind the 

 mouth (m). From the laying of the egg 

 to the full development of the Scyphos- 

 toma about eighteen months are required. 

 Although but a few weeks are necessary 

 for the development of all the tentacles, 

 yet several scarcely noticeable features are 



much slower in appearing, and do not, even when completely 

 established, produce a marked change in the external conforma- 

 tion of the Scyphostoma. Finally, however, toward the latter 

 end of the second year, a very perceptible transformation takes 

 place ; the body increases considerably in size, and seems to be 

 divided into several transverse rings, (fig. 35, d,) or superposed 

 discs. This is brought about by an actual self-division of the 

 body, which in process of time completely separates these discs 

 from each other and from the original stock. Before this takes 

 place, considerable change goes on in the discs ; first, their edges 

 become scalloped ; then each of the little lobes of the scallops, 

 growing longer, takes on a fork-shaped figure with two broad 

 prongs, and, at the same time, broad channels or tubes are hol- 

 lowed in the thickness of each disc, and a short funnel is devel- 

 oped from the centre, on the side toward the mouth of the parent. 

 In this condition the discs, one after the other, break loose from 

 the Scyphostoma, at its broader end, and swim freely in the 

 water, each an independent individual. 



At this period they go by the name of the Ephyra ; a name 

 which was originally given to them, before it was known that 



Fig. 36. The Ephyra of A urelia flavidula. Per. and Les. Six diameters. 

 A view from the mouth, or oral side, m, the four-sided proboscis, with the 

 mouth in the centre ; t, the broad, marginal, digestive canal, connected with the 

 central cavity (about r) by sixteen short, broad channels ; r, the four incipient 

 reproductive organs ; I, the ocular lappets ; o, the eye ; v, the lancet-shaped veil, 

 and the single, pointed tentacle. Original. 



