OVIPOSITION \N1> CHABACTEE OF THE EGG-CAPSU LES AND EGG. lO-'J 



cleavage, some of the embryos, however, develop no further, but 

 perish, their remains being devoured by the other embryos. This 

 is also the ease, according to McMubbich, in a few species of 



Crepi'liila, and in Uracil '/>//ix (Brooks). Fa-sciolaria lavs about 200 

 eggs in each capsule, but only I to 6 of these develop, and this is also 

 the ease with Buccinam widntum. Each capsule of Pur/jura lapiHus 

 contains 400 to 600 eggs, only 10 to Hi of which develop into mature 

 embryos (Selenka). The egg-capsule of Neritina fluviati/is also 

 shelters a large number of eggs i according to Blochmann 70 to 90) 

 although <>nlv a single embryo in it attains complete development 

 (Clapakede). In this case, the unfertilised eggs divide soon after 

 the polar bodies have formed, and break np into irregular heaps of 

 protoplasmic spheres, being in this way distinguished from the eggs 

 undergoing cleavage. 



In shape and structure, these egg-capsules vary greatly. As a 

 ride they are formed of tough leathery or parchment-like integument 

 and are in some cases approximately spherical, but appear flattened 

 on the side by which they are attached to foreign objects. This is 

 the case in Nerltin-i. the older cocoons of which easily divide into 

 two hemispherical halves. To allow the brood to escape, the capsule 

 occasionally has an aperture closed by a delicate membrane, situated 

 opposite to the point of attachment. Several capsules are usually 

 found together, as in r>n>-<-iinni< widatum, Fusus antiqnus and others, 

 the capsules of which are piled one upon another, thus forming an 

 enormous mass of spawn. They occasionally appear laterally com- 

 pressed and, in one species of F/isus observed by Bobretzky, are 

 round plano-convex discs, attached by the flattened side. The 

 capsules of Bitsycon (Ftdgur) also are leaf-like or rather disc-shaped; 

 these are arranged in a row like a roll of coins, and are attached to a 

 common filament. These capsules have an aperture opposite to the 

 points of attachment for the escape of the brood. 



hi Na,isa mutabilis, the capsules are cup-shaped and attached by 

 the obliquely truncated end, the opposite pointed end carrying an 

 aperture at first closed by a membrane. The surface of these capsules 

 shows polygonal markings which form rib like or membranous ridges. 

 They are found united into large clumps on sea-weeds and worm-tubes. 



The •cup-like capsules of many Prosobranchia are arranged in 

 groups attached by their narrow ends drawn out into stalks {Murex). 

 Here also, the aperture of the cup is closed by a membranous cover, 

 which opens when the brood is ready to hatch. In Purpura lapillus 

 10 to 1 •"> such capsules, which, however, are more Mask-shaped and of 



