128 Dr. W. B. Carpenter on the Development of Purpura. 



afresh, at my request, to the question of the development of 

 Pwyura, has just sent me the following notes, which I will 

 thank you to publish in your next Number : — 



"I. The egg-like bodies in the recently- separated egg-cap- 

 sules are destitute of any investing membrane, 



" 2. In those possessing a ' directive vesicle/ an envelope 

 appears very quickly ; and in such as are thus distinguished, the 

 segmentation is regular , and never in such sort as to give them 

 the lump-of-different-sized-cannon-shot-look (excuse my ter- 

 minology) which the vitelline spheres assume. The latter seg- 

 mentate frequently before the true ova, — I mean before those 

 possessing the ' directive vesicles.^ 



" 3. I have distinctly seen vitelline spheres from the agglomerated 

 mass pass through the oesophagus, and become united to the mass 

 within the embryo, I have made several drawings of the oeso- 

 phagus of embryos at different periods ; and I took care not to 

 look at yours first. They are so like as not to be worth sending 

 up, except that the aperture (when seen in front) appears more 

 nearly circular than in your figure. I could see right down 

 to the mass below. On subjecting a full embryo to pressure 

 (under the compressor) applied a tergo, the vitelline mass issues 

 through the cesophagus.^^ 



I venture to hope that I am now sufficiently exculpated from 

 the imputation thrown upon me by MM. Koren and Danielssen, 

 of having mistaken for an oesophagus the incipient foot. But 

 if further justification be necessary, I would beg to refer to the 

 memoir of M. Claparede (Miiller^s Archiv, April 1857) on the 

 development of Neritina fluviatilis, in which all my most im- 

 portant statements are borne out (express reference to them 

 being made) by the analogy of another species, and the co- 

 existence of a mouth and ciliated oesophagus with the rudimentary 

 foot is placed beyond all question*. It is not a little remarkable 

 that, according to M. Claparede, the observations of M. Lind- 

 strom, which have been cited by Messrs. Koren and Danielssen 

 as confirmatory of their views, are really coincident with his, 

 and therefore with mine, 



I am. Gentlemen, 



Your obedient Servant, 



William B. Carpenter. 



* An abstract of M. Claparede's memoir will appear in the next Number 

 of this Journal. 



