and the Winter-egg of the Bryozoa. 335 



in which it was formed, when the latter much exceeds the average 

 size of these cells, and the starch-grain appears to be developed 

 at the expense of the refractive granules, which at such times 

 are considerably reduced in number, if not in some cases alto- 

 gether absent. On other occasions the large graiii is replaced 

 by a great number of minute ones, as indicated by the applica- 

 tion of iodine, and lastly, as just stated, by amoi'phous starch. 



At an early period of the ovum (that is, long before the cel- 

 lular coat is formed), the spherical cells, though already filled 

 with the refractive granules, are few in number and subpoly- 

 morphic ; hence it may be reasonably inferred that their multi- 

 plication as the ovum increases in size is produced by fission : 

 the younger the ovum, the more polymorphic and resisteut are 

 these cells, while the older it becomes, the more they are attenu- 

 ated, and thus the more rapidly they burst by endosmose after 

 liberation. 



Winter-egg of Lophupus ? PI. VIII. figs. 8-15. 



Matured form compressed, oval, slightly bent upon itself both 

 transversely and longitudinally like the brim of a hat, convex 

 and elliptical in the centre, but more so on one side than 

 the other, thinning all round towards the margin, which is 

 slightly irregular and bordered at the ends only by cirrhous 

 appendages. Composed from without inwards of — 1st, the 

 cirrhous appendages; 2nd, a cellular coat, fiat, unequal in 

 thickness, consisting of thin horny cells arranged in long or 

 short hexangular prisms according to their position, in lateral 

 contact ^\dth each other on all sides, and perpendicular to the 

 surface of (3rd) a coriaceous coat, subelliptical, and surrounded 

 subequatorially by a thin rim of the same substance, which is 

 extended to the margin of the egg all round, and thus divides 

 the cellular coat horizontally into two parts, enclosing a great 

 number of spherical transparent cells filled Avith minute re- 



When the "winter-egg" is crushed, the spherical transparent 

 cells, which are very thin, burst by watery endosmose ; and then 

 their contents are seen to consist of refractive granules, a])pa- 

 rently of an elongated elliptical form, which vary in size from 

 l-21600th of an inch, which is the length of the largest, 

 to immeasurable minuteness, and all present, on issuing, the 

 vibratoiy motion noticed in the minute granules of the spherical 

 cells of Spongilla, to which I have already alluded ; but even 

 the largest of these granules are too small for me to state 

 whether, like the larger refractive granules of Sjiongilla, they 

 also present the appearance of budding. 



