DIOECIOUS MOLLUSCA. 



359 



of an elliptical vase supported on a short stalk, and adhering 

 by a broad base to a common membrane spread over the sur- 

 face of the shelving rock, from which it hangs in clusters of 

 considerable extent, sometimes covering a space eight inches 

 square. " When they are first taken out of the sea, they are 

 of a bright semi-transparent yellow colour, of a horny tough 

 nature, containing a viscid substance, with many orange- 

 coloured seeds, or egg-like particles, in the upper part of each 

 cup," which, you will observe from (Fig. 74, d, is lined with 

 a thin inner membrane similar to what we have described in 

 the ovarian capsule of Fusus antiquus ; and remember that 

 every nidus of every Gasteropod of this tribe is similarly 

 constructed. In due time, the "orange-coloured seeds" 

 have become fcetal Purpura?, when the apex of the cup rises 

 to a more convex form, becomes thinner, " and after about 

 four months opens, and the young prisoners escape into the 

 surrounding medium, and take refuge in the crevices of the 

 rocks, or amongst mussels, balani, &c, which are attached 

 to them. The young leave the cups gradually, and some- 

 times a fortnight elapses between the exit of the first and 

 the last, and they are of different sizes ; they have all the 

 peculiar habits of the adult ones, such as the remaining out 

 of the water for long periods : this I observed in many that 

 I reared in a dish in my house ; some of them, also, 

 were of a purple colour." f Here is the effigies (Fig. 75) 

 of another nidus of equal simplicity, and a member also of 

 Lund's Order i., Class II. Fig. 75. 



It belongs to the Nassa 

 reticulata, and all the 

 specimens I have seen 

 have been deposited on 

 the fronds of shore sea- 

 weeds, or on the grass- 

 like leaves of the Zostera 

 marina, arranged some- 

 times in no obvious order, 

 but usually in a row so 

 close that, when depress- 

 ed, they overlie each 

 other like the brass scales 

 of the cheekband of a 

 hussar. Mr. Peach compares them to the spade on play- 



f Peach in Report Brit. Assoc. 1842, p. 66 ; and in Ann. and Mag. Nat. 

 Hist. \\. 29, pi. 1, fig. 1 — 3. I entirely dissent from my friend's conclusion 

 that Ellis believed the sea-cup to he the nidus of Littorina littorca. No 



