1884.] NATURAL SCIENCES OP PHILADELPHIA. 195 



life may have quickened their long dormant cells, was hidden 

 from sight by the opaque chitin of theii' valves, to that in which 

 these had been pushed off to right and left and the neophite had 

 reached forth to discover the nature and limitation of the new 

 scene into which he had entered. 



The statoblasts, as in the other species of this genus, are orbic- 

 ular, reddish brown in color, relatively thick, with rounded 

 marginal annulus and a double series of retentive hooks. The 

 latter spring from circular membranous lines on each side, near 

 the circumference of the chitinous body, and on one side are 

 reflexed from the margin, while those pertaining to the other 

 curve abruptly, partly around the annulus and then become radial 

 in the equatorial plane ; their surfaces are i-oughened or minutely 

 tuberculated. Little difference is noticeable between the diameters 

 or the degrees of convexity of the exposed sides of the statoblast ; 

 that, however, to which the longer bent booklets are attached, is 

 generally the larger, with a single sweeping curve, while the other 

 has often a higher convexit}' at its centre. The chiton is com- 

 posed of minute hexagonal cells whose outer surfaces appear to 

 be concave^ or depressed, but their margins are elevated here and 

 there at the angles, into spinous papillae, with rounded apices, 

 more numerous near the circumference of the statoblast. 



As the germination of the enclosed embryo progresses the sides 

 or valves are forced apart, separating always at the same portion 

 of the margin ; the whole annulus remaining attached as before 

 described, while the chitinous rim of the other is drawn out from 

 under it, as a pill-box is separated from its lid. This is in marked 

 contrast with the process by which the valves of Pectinatella are 

 separated, as shown in the accompanjang diagram. 



The rounded edge of the semitransparent coenoecium now 

 appears and slowl}^ protrudes itself so that it is some hours before 

 the first polypide projects his immature tentacles. In the begin- 

 ning, and sometimes for several days, the coenoecium is nearly 

 filled with granular particles of 3^olk-like matter, opaque b}^ trans- 

 mitted light and of a light waxen yellow ^ when reflected light is 



^ Prof. Alhnan describes the chiton cells of C. macedo as convex upon 

 their outer surface which thus become "elegantly mammillatecl." A trans- 

 verse section of the statoblast shows that the annulus is firmly attached to 

 that side on which the hooks are reflexed, and spreads broadly over the rim 

 or margin pertaining to the opposite valve. 



'^ These are white in Pectinatella. 



