1 6 Dr. W. B. Carpenter on the Development of Purpura lapillua. 



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

 Development of Purpui*a 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, 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, 

 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 

 doubleor 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 difference is 

 still more strongly marked in 

 the subsequent divisions ; for 



whiUf i'Ue' plpnvno-p nt tViP ^"'^ stages of embryonic development of 



WnilSt me Ciea\age or Cne purp„ra lapUhis-. a, cgg-Uke spherule; B, c, 



Volk-SpheruleS goes on irre- ^' ^> <^> successive stages of segmentation of 



•',,^ ~,.., , yolk-spherules; d, h, i, i, k, successive stages 



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



Fis. 1. 



