138 Dr. G. C. Wallich on the Value of 



contractile vesicle is in direct communication with the vacuolated 

 sarcode around. 



Owing, doubtless, to an unintentional alteration of my de- 

 scription of the contractile vesicle of A. villosa, Mr. Carter 

 makes it appear, however, that I assume the possibility of its 

 formation as in the case of spontaneously formed vacuoles, at 

 any portion of the body. Thus (Annals, July 1863, p. 39) it 

 is stated that I regard "all these dilatations as extemporized 

 vacuoles;" whereas I draw a marked distinction (Annals, June 

 1863^ p. 439) between the contractile vesicle, to which I refer as 

 " a specialized vacuolar cavity," the " food- vacuole, which is in- 

 variably formed at the surface," and those endogenous vacuoles 

 which appear and disappear spontaneously within the substance 

 of the organism [lac. cit. p. 436). The grounds for these dis- 

 tinctions will become manifest as I proceed. Meanwhile I would 

 direct particular attention to the definition of the contractile 

 vesicle given by Dr. Carpenter (* Introduction to the Study of the 

 Foraminifera,^ p. 14), namely, " a vacuole with a definite ivall," 

 inasmuch as I shall hereafter endeavour to prove that to this 

 extent only can it, with propriety, be regarded as a distinct 

 structure. 



In allusion to my remarks in the 'Annals' for June (p. 439), 

 Mr. Carter says he is glad to find that I support him in the 

 opinion that the contractile vesicle of Amoeba discharges itself 

 externally. As stated in the 'Annals' for June (p. 441), it wdll 

 be seen that I had also satisfied myself of the fact with regard 

 to an Infusorial animalcule. It is right, however, to mention 

 that, so long ago as 1849, Dr. 0. Schmidt asserted that the 

 contractile vesicle in Actinophrys opens externally — although 

 Dr. Lachmann, from whose writings I obtain this piece of in- 

 formation, is of a contrary opinion *. But Mr. Carter inadver- 

 tently omits to state that the determinate portion of the body 

 in Amoeba at which the discharge of the contractile vesicle takes 

 place was pointed out, for the first time, as observed in A. vil- 

 losa ; for when I quoted his very graphic description of the ac- 

 tion of this organ as occurring in Amoeba and Actinophrys 

 (Annals, 1856, vol. xviii. p. 126), I was certainly under the im- 

 pression, from what was advanced in the same place (see next 

 paragi'aph), that, in indicating a definite spot at which the dis- 

 charge takes place in Amoeba, my opinion was at direct variance 

 with his. Thus, although Mr. Carter, in his recent paper (An- 

 nals, July 1863, pp. 38 & 39), says, " It is a remarkable fact, that 

 although the vesicula is borne round the interior of A. princeps 



* Dr. C. F. J. Lachtnann on the Organization of the Infusoria (Ann. 

 Nat. Hist. 1857, ser. 2. vol. xix. p. 22/). 



