146 DISCOPHOR^. Part III. 



the structure of the lasso-cells of Hydra, with a neck and hooks at the base of the 

 thread (e), or the thread may be simple {d). The 1jags of the cells themselves are 

 slightly pear-shai^ed. The variety of these appendages may be appreciated by 

 comparing those represented, Ftffs. 8, 9, 10, and 11. I have noticed an unexpected 

 difference between these appendages in the two sexes. In the males (PI. XIII. 

 Fiff. 2, vi, and PL XIII*. Fiff. 5, d') they are much more uniform than in the females, 

 in which they exhibit the greatest variety of appearance (PI. XIII. Fiff. 2, /). 

 What may be the function of these singular organs I am at a loss to say ; the 

 constant difference which I have noticed among them, in the two sexes, justifies 

 the inference that in some way or other they must be connected with the laying 

 of the eggs and the diffusion of the spermatic particles. 



I have already stated, that the sexual organs project into the main cavity, and 

 that the eggs make their escape from that cavity outAvard, through the four small 

 openings alternating with the genital pouches. When mature, the eggs rise from 

 the stroma of the ovary like beads (PI. XIIP. F/(/. 22) ; they are surrounded by a 

 chorion which forms a neck, connecting them with the walls of the genital organ. 

 When the eggs are fully mature {Fiffs. 18 and 19), this neck breaks, and forms a 

 large micropile above the germinative vesicle. In younger eggs {Fiff. 20) the sacs 

 containing the eggs are pear-shaped, and the neck slender; this grows shorter and 

 wider {Fiff. 21) as the eggs enlarge. The spermatic sacs {Fiffs. 16 and 17) have 

 the same structure ; the spermatic particles themselves have the form of an arrow- 

 head, with a long, slender thread. The eyes have the usual form and structure 

 observed among our common Discophora3 ; they are short, hollow peduncles, with 

 a round, faceted termination (PI. XIIP. Fiffs. 11, 12, o o, 13, 14, and 15). Occasion- 

 ally two eyes are developed, side by side {Fiff. 8, o^ o^), there being an eye at 

 the termination of each fork of the radiating tube of their respective segments. 



The gelatinous disk is flat, comparatively thin, and gradually tapering in its 

 thickness, from the centre to the margin (PI. XIIP. Fiff. 2). In the central part, 

 on the lower side, corresponding to the main cavity, it is slightly thinner than 

 at the point from which the lower floor recedes from the disk, to form the acti- 

 nostome. A magnified section, Fiff. 3, shows that the gelatinous disk, y, is traversed 

 by numerous fibres, in a vertical direction, across its whole thickness, and that the 

 lower floor, o, is comparatively thin; between the two is the layer a% traversed 

 by the radiating chymiferous tubes. 



The generic characters of Polyclonia, I believe, consist in the peculiar mode of 

 ramification of the arms, which are deeply divided to the base of the central 

 cavity, and then unite, two and two, upon the lower floor of the main cavity. 

 The strong, ramified branches of these arms, are no doubt also generic, as well as 

 the different kinds of lobes and appendages along their soldered margins, and upon 



