16 Dr. W. B. Carpenter on the Developmmt of Purpura lapillus. 



III. — Remarks on MM. Koren and Danielssen's Researches on the 

 Development of Purpura lapillus. By Wm. B. Carpenter, 

 M.D., F.R.S., F.G.S., F.L.S. 



Although I have for some time had in my possession the 

 Second Part of the ' Fauna littoralis Norvegise/ containing the 

 second memoir of MM. Koren and Danielssen on the develop- 

 ment of Purpura lapillus j yet it was not my intention to take 

 any notice of their criticisms upon my observations, until I 

 should have had the opportunity of again working through the 

 subject. As the views of those gentlemen, however, have 

 recently been brought prominently before the readers of the 

 'Annals^ (see vol. xix. p. 433), and as my own have not been 

 presented in its pages, I take the liberty of drawing attention to 

 the following concise summary of them; referring such as desire 

 a more detailed statement to the original memoir in the 'Trans- 

 actions of the Microscopical Society,^ new series, vol. iii. 



It will be remembered that, according to MM. Koren and 

 Danielssen, all the 500 or 600 egg-like bodies contained in any 

 one capsule are of similar character : all undergoing coalescence 

 into a conglomerate mass ; and this mass subdividing itself into 

 ovoidal bodies of larger or smaller size^ each of which becomes 

 converted into an embryo. 



My view of the case is very different. Of these 500 or 600 

 egg-like bodies, I regard a small number only — usually from 

 12 to 30 — as true ova, the remainder being only yolk-spherules y 

 which are destined to serve for the nutrition of the embryos. 

 The distinction between them manifests itself at a very early 

 period, even in the first segmentation; for while the yolk-sphe- 

 rules divide into two equal hemispheres (fig. 1, b), the real ova 

 divide into a larger and a 

 smaller segment (d) ; in the ^^' 



cleft between these are seen 

 the minute 'directive vesicles,^ 

 which appear to be always 

 double or even triple, although, 

 from being seen 'end-on,' 

 only one may be visible; 

 and near these is generally to 

 be seen a clear space in each 

 segment. The difi^erence is 

 still more strongly marked in 

 the subsequent divisions ; for 



whilst the rleavao-P of fhp ^^''^^ **^^^* °^ embryonic development of 



WnilSl tne Cieavage OI tne purpura lapUlus-. a, egg-like spherule; b, c, 



yolk-spherules erOeS on irre- ^» ^' «» successive stages of segmentation of 



•'ii^ T'T 1 yolk-spherules; d, h, i, j, k, successive stages 



gUlarly, so as to divide each of development of early embryos. 



9 % % 



