134 



MELICEllTUM CAMPANULA. 



(Fig. 209), and taper rajiidly ; they are thickly covered with lasso- 

 celk. 



Artificial fecundation of these MedusfE can be very readily made by 

 keeping males and females for a day or two together in a glass jar, 

 when we shall find, swinnning near the bottom, innumerable spherical 

 embryos (Fig. 210), in which the spheres of segmentation are still 



Fig. '212 



Fig. 213. 



visible ; these elongate (Fig. 211), a cavity is formed at the blunt end, 

 and Ave have a somewhat pear-shaped embrj'o, strongly ciliated, with 

 walls of uniform thickness (Fig. 212), swinnning about with great ve- 

 locity ; these embryos attach themselves by the blunt end (Fig. 213), 

 and soon elongate, as in the two middle figures of Fig. 213 ; the slen- 

 Fig.au. der extremity next swells (Fig. 214), and this is the 



first trace of the sterile Hydra head. The wall of 

 this swelling soon becomes somewhat indented, as 

 in Fig. 214, where we have some of the successive 

 stages of the sterile H3'dra, until it forms a small 

 horny bell, covering only the base of the long, ster- 

 ile Hydra head, which terminates Avith ten stout, 

 short tentacles, connected by a Aveb. This Hydra- 

 rium differs considerably from that of Lafoea, but it 

 still has sufficient resemblance to shoAV their con- 

 nection ; it is one of the easiest to raise, the 

 Planula3 are very hardy, and the development of 

 the Hydrarium is readily folloAved. It groAvs in 

 small tufts, Avhich after six months had not attained a greater height 

 than one third of an inch. 



Greenland (Fabricius) ; Massachusetts Bay (Agassiz). 

 Cat. No. 351, Grand Manan, L. Agassiz. Medusa. 

 Cat. No. 373, Nahant, 18G3, A. Agassiz. Medusa. 

 Cat. No. 448, Nahant, 1864, A. Agassiz. Medusa. 



Fig. 210. Spherical cmliryo. 



Fig. 211. The same, somewhat more advanced. 



Fig. 212. The same, immediately before becoming attached. 



Fig. 213. Group of embryos attached, in different stages of development. 



Fig. 214. Different stages of growth, beyond those of Fig. 213, till the sterile Hydra is fully 

 developed. 



