244, 
MEM. M. C. Z., IX. No. 3.— ACALEPHS, POLYPS. 21 
the branch has been completed, and the portion thus separated has almost freed itself from the branch. 
y. A body of ccenosare (frustule) has dissolved its connection with the hydroid, and become a free planula- 
like body swimming in the water. 
. Hydroid formed by a gemmation from the free frustule. 
24°, 
The frustule (y), after swimming about in the water, secretes a mucus tube (4), into which it is represented 
in the figure as partially drawn on the right hand side (of figure). 
A bud has been sent out from the extremity of the frustule (ym). This bud increases in size, and ultimately 
forms the hydroid, with hydranth (24°). From the side of this hydroid a branch (7) is emitted. 
25"-25°, Development of a Corbula in the family of Plumularide. From Allman, op. cit., p. 60. 
25%-25°. Aglaophenia plwma, 
. A very young corbula. J. vm. Lateral branch. 
. Older stage of the ecorbula, with the ovarian vesicles (oa. vs.) already formed as spherical sacs, arising from 
the midrib of the corbula, between the lateral rami (7. rm). 
. The same, older. oa. vs. Ovarian vesicles, called gonangia. J. rm. Lateral rami (coste.) hyth. Single 
hydrotheca. 
. Mature corbula. The serrated bodies along the sides are called nematophores. The corbula is a specialized 
basket-shaped structure found in certain sertularian hydroids, for the protection of the vesicles and their ova. 
26. Young Cyanea arctica, showing the umbral papillae. From Fewkes, Studies of the Jelly-fishes of Narragan- 
sett Bay, Bull. Mus. Comp. Zodl., Vol. VIII, No. 8, Pl. VII. fig. 1. 
