4s4A Dr. G. C. Wallich on Amoeba villosa 



occasionally to form an elongated, transparent, mammilliform 

 eminence, which, at the moment of contraction, subsides pre- 

 cisely like a blister of some soft tenacious substance that has 

 been pricked with a pin"*. Mr. Carter does not mention any 

 special excretion — that is to say, whether he means the excretion 

 of effete nutritious matter or water only. If the latter, I en- 

 tirely agree with him — my view being that, whilst the general 

 substance of the body absorbs water from the surrounding me- 

 dium by endosmotic action, and partly also by admission en 

 masse into the extemporized food- vacuoles ; through the agency 

 of the opposite or exosmotic action the fluid is poured into the 

 contractile vesicle, gradually distending it, as described, until 

 rupture ensues. The moment that the tension on the most pro- 

 minent and, consequently, the most attenuated portion of the 

 vesicle is relieved by the escape of its contents, the orifice be- 

 comes obliterated by the union of its edges, and the process is 

 repeated. In this sense, then, the contractile vesicle may be 

 regarded as a true water-vascular and excretory organ. I need 

 only add that, according to my own experience, and in ac- 

 cordance with the opinion expressed by several eminent ob- 

 servers, the contractile vesicle takes no share, under any circum- 

 stances, in the capture, inception, or extrusion of any solid 

 substances. 



In a former page, allusion has been made to a mode of repro- 

 duction which, although closely bordering on simple gemmation, 

 must, I think, rather be regarded in the light of viviparous 

 parturition. I had never noticed it prior to my recent and almost 

 continuous observation of the Hampstead Amoeba, nor am I 

 aware that it has previously attracted the attention of other 

 naturalists, although M. Jules Haime records examples amongst 

 the Infusoria in which minute bodies ejected from the body of 

 the parent have become converted into young animals whilst 

 still under observation f. In Amoeba, however, such an oversight 

 may easily be accounted for by the circumstance that the newly 

 liberated individuals are so minute, in comparison with the 

 parent form, as to be barely distinguishable unless examined 

 under high powers and with a knowledge of their origin. They 

 rarely measure more than 2jo o^^ ^^ TeVlT^^ °^ ^^ ^^^^ ^^ their 

 most extended state, and yet, when carefully analysed, exhibit 

 nucleus, contractile vesicle, villous tuft, and even protoplasmic 

 granules, with every distinctive character discernible in the parent 

 from which they sprang. It is also a very significant and re- 

 markable fact, that, even in this minute stage of their existence, 



* Ann. Nat. Hist. ser. 2. vol. xviii. p. 126. 



f Carter on the Organization of Infusoria (Ann. Nat. Hist. ser. 2. 

 vol. xviii. p. 223. 



