CHAP, iv.] THE VOYAGE HOME. 195 



These special spines are cylindrical, and nearly smooth, and 

 they lean over toward the anal opening, and form an open tent 

 for the protection of the young, as in Cldaris nutrix, a species 

 presently to be described, but at the opposite pole of the body. 

 In this species the eggs are extruded directly into the marsu- 

 pium ; and I imagine, from the very small size of the ovarial 

 openings, that when they enter it they are very minute, and 

 probably unimpregnated. In the examples which we dredged 

 at the Falkland Islands, the young were, in almost every case, 

 nearly ready to leave the marsupium ; we were too late in the 

 season to see the earlier stages. Young in the 'same marsupium 

 are nearly all of an age, some somewhat more advanced than 

 others. The diameter of the test is from 1 to 1-5 millim., and 

 the height about*"8 millim.; the length of the primary spines 

 is, in the most backward of the brood, '5 millim., while in the 

 most advanced it equals the diameter of the test. The perisom, 

 in which the cribriform rudiments of the plates of the corona 

 and the young spines are being developed, is loaded with dark- 

 purple pigment, which makes it difficult to observe the growth 

 of the calcareous elements. About thirty primary spines arise 

 on the surface of the corona almost simultaneously in ten rows 

 of three each : they first make their appearance as small papil- 

 lae covered with a densely pigmented ciliated membrane ; and 

 when they have once begun to lengthen, they run out very 

 rapidly until they bear to the young nearly the same propor- 

 tions which the full-grown spines bear to the mature corona. 

 Very shortly some of the secondary spines, at first nearly as 

 large as the sprouting primary spines, make their appearance in 

 the interstices between these ; and a crowd of very small spines 

 rise on the nascent scales of the peristome. Successively five 

 or six pedicellariae are developed toward the outer edge of the 

 apical area, which at this stage is disproportionately large ; the 

 pedicellarise commence as purple papillae, which are at first un- 

 distinguishable from young primary spines ; the first set look 



