a new Group of Parasitic Crustacea. 45 



treinities of which are also frequently sinuous. On the dorsal 

 surface of the disk, which is turned towards the tail of the Por- 

 cellana, there are often smaller prominences, similar to the above 

 lobes, near the margin. On the ventral surface, which is turned 

 towards the sternum of the Porcellana, the eye is first struck by 

 the ovary (PL II. fig. 2, b), which occupies nearly the whole sur- 

 face up to the origin of the marginal lobes, but has posteriorly 

 a broad and shallow sinus, and anteriorly a narrow emargination 

 dividing it halfway down, and dilated into a clavate form at the 

 posterior end. 



Below the ovary (nearer the ventral surface) and near the 

 anterior margin of the disk, there lie two very considerable 

 roundish or reniform glands (fig. 2, c), of that peculiar translu- 

 cent appearance that so frequently characterizes the testes of the 

 lower animals ; their efferent ducts, which are at first narrow, 

 but afterwards dilated, very thin-walled and difficult to trace, 

 run backwards on their inner side. I suppose that they open at 

 the hinder margin of the ovary in the brood-chamber, which 

 will have to be mentioned immediately. Likewise under the 

 ovary, and corresponding therewith in its outlines, but filling up 

 the anterior notch, there stretches a cavity with delicate walls, 

 containing a reddish transparent fluid : that it is a single cavity 

 is evident when it contracts,; in the extended state, one might 

 be misled into assuming the presence of a network of tubes 

 passing between the separate groups of eggs, issuing from a 

 vesicle situated in the anterior notch of the ovary, the colour of 

 the thin stratum of fluid over the more prominent eggs becom- 

 ing almost imperceptible, and distinct only in the furrows between 

 them. 



In the posterior sinus of the disk there is a considerable orifice, 

 surrounded by a notched margin (fig. 2, a), through which water 

 is seen to flow in and out with an alternate extension and con- 

 traction of the body. It leads to a wide brood-chamber, the 

 extent of which is most easily ascertained when it is inflated 

 by means of a fine-pointed glass tube : it is then seen to occupy 

 the whole dorsal surface, except the anterior notch of the ovary, 

 and to extend into the marginal lobes, which are merely diverti- 

 cula of it. The brood-chamber is usually found fully distended 

 with eggs, which adhere especially to its outer wall, and are all 

 of the same age. When they approach maturity, the margin of 

 the disk appears more transparent, and finally the marginal 

 lobes and back are covered with black points, from the eyes of 

 the young brood, which swims out simultaneously. Two days 

 after the swarming, I again found in one animal fresh ova, in 

 course of complete segmentation in the brood-chamber. The 

 water flowing into the brood-chamber serves, in my opinion, 



