Chap. I. 



REPRODUCTION OF CORYNE MIRABILIS. 



19/ 



As the medusa grows older, the tentacles (PI. XVIII. Fig. 14, and wood-cut 

 17,/) curl themselves within the cavity of the disk. They are prevented fi-om 

 coming in direct contact with the inner surface (c) 

 of the cavity and the procoscis (c^), by the trans- 

 verse septum (c*), which is forced inwai'ds with them. 

 The tentacles might very naturally project outwardly, 

 were it not that they are restrained from doing so 

 by the prolongation of the horny sheath of the h}'- 

 droid, which envelopes the medusce very closely with 

 a thin film (//). The base of each tentacle is swollen 

 into a large bulb (f?), the interior of which contains 

 a cavity of considerable capacity {h^). Here the radi- 

 ating and circular tubes mutually empty, and here 

 the chymiferous fluid keeps up a continual whirling. 

 At the base of each tentacle, on the outer side, there 



is a small black mass {c) imbedded in the outer wall. This spot, being in the 

 same position as the eye in the adult, must be that organ. The transverse septum 

 (c*) is very thin, except at its peripherj^ (f") ; in fact, it is not possible, in a profile 

 of its thickness, to see its three component walls. It has great extensibility, and. 

 judging from its numerous wrinkles, it must be in a very lax state, although 

 pushed inwards by the tentacles. The outer («), middle (i), and innermost walls 

 (c), are much thinner than in the last phase, not only absolutely so, but in pro- 

 portion to the size of the disk. The proboscis {I? c^) offers nothing remarkable 

 or noteworthy, except, perhaps, that it possesses the power of enormous distension, 

 such as has never been noticed in the free medusas. As we might naturally 

 suppose, from the present relations of the medusa to its hydroid, the proboscis 

 has no opening at the end. 



At this time the medusa begins to contract more rapidly, and occasionally with 

 a sudden jerk. The frequency of these jerks increases, as the animal grows older, 

 till very often thi'ee or four succeed each other in rapid succession. The envel- 

 oping horny film at last is torn open, and allows the medusa to expand more 

 freely, and the tentacles to withdraw themselves from the cavity of the disk, and 

 stretch outwardly. The transverse septum becomes perforated, in the centre, by 

 a hole which rapidly enlarges, till, by the time the medusa has been free two or 

 three days, it equals about one fifth (PI. XVIII. Fig. 17, a) of the diameter of 

 the disk. This hole gives ingress and egress to the water, which is forced out 

 as the disk conti'acts, and rushes in as the disk expands ; at the same time the 

 transverse septum is pushed inward or outward, according to the direction in which 

 the water is running. In order to free itself, the peduncular attachment (PI. XVIII. 



