334 Mr. H.J. Carter on the Seed-like Body 0/ Spongilla 



Plumatella repenSy Van Ben.*, growing on a floating cork in the 

 midst of Spongilla cinerea and S. Meyeni, which were spreading 

 themselves over the same body ; and in the tank where now the 

 Lophopus abounds, Spongilla Carteri (for such I shall henceforth 

 term this species, in accordance with Mr. Bowerbank's proposi- 

 tion) is also growing in the greatest profusion, almost to the 

 total exclusion of all the other species. Let us now proceed to 

 the description of the ovum and winter-egg of these organisms 

 respectively, commencing with the former. 



Ovum of Spongilla Carteri. PI. VIII. figs. 1-7. 



Matured form spherical, presenting a round infundibuliform 

 hilum or hole leading into the interior, to which in many in- 

 stances the remains of a funiculus may be seen to be attached, 

 composed from without inwards of — 1st, a coating of loose, 

 smooth, slightly curved, pointed, silicious spicula; 2nd, a 

 cellular coat, spherical, of equal thickness all round, except 

 where pierced by the hilum, consisting of thin horny cells 

 arranged in hexagonal columns in contact with each other 

 on all sides, and perpendicular to the surface of (3rd) a coria- 

 ceous coat, spherical, thick, tough, homy, of a yellow colour, 

 which encloses a great number of spherical transparent cells 

 partially filled with refractive granules, among which are 

 starch-grains. 



When the ovum is crushed, the spherical transparent cells, 

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

 granular contents are seen to consist of a number of transpa- 

 rent, refractive, compressed, lenticular cells, which vary in size 

 from 2-5400ths of an inch, which is the long diameter of the 

 largest, to immeasurable minuteness; while the latter, for a 

 considerable time after issuing, keep up a continued vibratory 

 motion (like the recently ejected mucus-granules of living cells 

 generally) around the former, which remain stationary. The 

 larger granules or cells also frequently present one and some- 

 times two smaller ones attached to them, indicative of their 

 multiplication being produced by budding. 



On the other hand, the starch-grains, which resemble those 

 of wheat, being subelHptical, compressed, thin, and marked 

 with concentric circular lines, vary in number and size, being 

 frequently much larger than the spherical cells in which they are 

 originally formed, and from this passing down to immeasurable 

 minuteness, and occasionally into amorpho,us starch. Sometimes 

 a large starch-grain may be seen still within the spherical cell 



* P. stricta, AUman, * Freshwater Polyzoa,' p. 99, Ray Society's Publi- 

 cations. 



