mmediately distinguished from the polype cells, by the 

 irregularity ot their distribution, their greater size and by 

 their being urn-shaped, having narrow bases by which they 

 are attached to the polypidom, and contracted and terminal 

 apertures through which the gemmules escape into the sea. 

 These vesicles when first formed, are filled with a granular 

 pulp of an uniform consistence ; it soon, however, gets dark 

 towards its centre and decreases in bulk, leaving the sides of 

 the vesicle free; the pulp now looks like a central column 

 running from the base to the neck, which is closed. The 

 pulp still bears the appearance of the central pith or of a 

 rudimentary polype, without a mark to indicate the forma- 

 tion of the gemmules ; and up to this point the formation of 

 the gemmules is alike in all the Sertvlariadce, though they 

 differ in some measure afterwards. In the Laomedea geni- 

 culata the surface of the pulp soon gets furrowed and marked 

 into indistinct globules with a darkish centre; and as de- 

 velopement goes on the gemmules get more distinct from 

 each other, and the central dark spot of a deeper tint, more 

 de6ned, and the part surrounding it more transparent, resem- 

 bling the albuminous zone of the common egg ; and they 

 finally escape in this manner, till all the pulp contained in the 

 vesicle has been converted into reproductive gemmules. In 

 a kindred species, the L. gelatinosa a different method is 

 pursued. Iu it the pulp 611s the vesicle as in the case above, 

 and the surface becomes marked and irregular, forming the 

 first appearance of the future germs. They then appear more 

 distinctly, and as if formed from the pulp itself; they rapidly 

 get more and more defined, and stand in relief from each 

 other, remaining attached to the central placental column by 

 minute umbilical cords. These cords getting more and more 

 attenuated are finally ruptured and the gemmules float at 

 liberty within the cell. The vesicles being closed, the 

 gemmules are hindered from escaping; but, whether from 

 pressure or a vital process, the upper portion rapidly gets 

 thinner and more transparent and is finally ruptured, the 

 gemmules then escaping into the surrounding fluid. Judging 

 from a figure of Ellis' it would appear that a polype is some- 

 times formed in these vesicles ; and Jones in his " Outlines 

 of the Animal Kingdom" has given a similar figure with an 

 explanation ;* such an appearance, however, I have never 

 seen, though I have examined hundreds, or perhaps thou- 

 sands of living specimens. The reproductive gemmules, 

 which are now at liberty, are rapidly whirled about from 

 place to place, stopping occasionally as if in search of a 

 situation on which to fix. The motions of these minute 



* Pat;e 46. 49. 



