S56 



DICECIOUS MOLLUSCA. 



that it affords entrance to nothing excepting tlie water wliicli 

 is necessary to aerate the growing young (a).* Within this 

 pericarp, and only very loosely connected with it, there is 



Fig. 71. 



m vf it 4; 



T 



a bag of a similar form (b), but everywhere close, and of such 

 a thin and pellucid membrane that it presents no obstacle to 

 the influence of the oxygenating medium. At first its con- 

 tents are fluid and granular, but soon opacities are to be 

 discovered in several places, and ultimately from two to six 

 young are developed in each pouch, which can only make 

 their way out, at the appointed time, by a rupture or 

 dissolution of the inner bag. Still more singular are the 

 concamerated nests of many exotic zoophagous Gasteropods. 

 Here is the figure (Fig. 72) of a portion of one which seems 

 to have afforded Mr. John Winthrop the subject of the fol- 

 lowing notice : — " Moreover," he says, in describing some 

 curiosities he had sent to the Royal Society, " there are 

 some of the matrices, in which those shels are bred, of which 

 the Indians (American) make the white wampanpeage, one 



* Baster says that it admits neither air nor water — " quse aeris aquseque 

 marinfe ingi-essuni arcet, sed quje exitum foetu maturo ex ovis concedit." — 

 Opusc. Subs. i. 37. tab. v. fig. 3. 



