Chap. IV. PARYPHA CROCEA. 257 



in those medusoids which have set free nearly all their young {Fig. 14), removes 

 all possibility of mistake. 



At birth, and for a short time before that period, the tentacles of the lower 

 row are very differently proportioned from those of the adult, both in regard to 

 the general contour, and in the relative thickness of their walls. In the adult 

 stage, as we have shown on a former page (p. 251), the tentacles gradually taper 

 to a rounded or slightly swollen tip, and are four-sided, but at birth they are 

 round, and although they taper like those of the adult, yet, at the end, they 

 terminate in a large globular expansion {Fig. 26, c), which is densely crowded with 

 lasso-cells. This globular tip has nearly twice the diameter of that portion of the 

 tentacle which is immediately below it. The outer wall {a) of the tentacles has 

 about one sixth the thickness of the inner one {b), and is exceedingly transparent, 

 so that it has not been possible, with the microscopic powers which we had at 

 hand when these observations were made, to see the nature of its cellular structure. 



Proles medusoidea. — The peduncle, which forms the basis of each group of 

 medusoids, has hardly begun to bud from the convex upper walls of the stomach, 

 before the young medusoids appear. At first, each medusa-bud is a low projection 

 {Figs. 3 and 3") of the double wall {a b) of the peduncle, and embraces a broad 

 cavity {c) which is in direct communication with the chymiferous channel of the 

 latter. This prominence increases in height, until it is considerably higher than 

 broad, before any change takes place in the relation of the outer and inner walls 

 {Figs. 4 and 4"). Then the outer wall grows faster than the inner one, and the 

 two consequently become separated and leave, between them, a space (PI. XXII. 

 Fig. 1, ef which is filled by a substance which, in the female, we have called the 

 germ-basis,^ and, in the male, the spermatic mass. The inner wall, in the meanwhile, 

 becomes cup-shaped at the end, next the germ-basis, by rising in the form of a rim 

 {Fig. 1, b) closely pressed against the outer wall («). The edge of the cuj) rises very 

 rapidly, so that its edge (PI. XXIII. Figs. 5 and 5% b"^) nearly reaches the end of the 

 medusoid before any other change occurs in the development of the embryo. In 

 this way the germ-basis becomes almost completely enclosed in double walls {Fig. 5", 

 a b). This new inner wall (i^) is nearly twice as thick as the outer one (a), 

 and comes to a sharp edge (i^) at its outer end, where it forms the rim of the 

 cup. Immediately after this the bottom {d^) of the cuj) rises gradually, as if 



^ There are certain phases in the development ^ We have already described, on a previous 

 of the medusoids of Thamnocnidia spectabilis which page (p. 254), the nature of the substance which 

 resemble those of Parypha crocea, and on this fills this space, and, subsequently (p. 255), shown 

 account the figures of the former may be used to why we have given it the name of the germ- 

 illustrate the latter. basis. 

 VOL. IV. 33 



