THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



[THIRD SERIES.] 

 No. 71. NOVEMBER 1863. 



XXXII. — Further Observations on the Distinctive Characters and 

 Reproductive Phenomena of the Amoeban Rhizopods. By G. C. 

 Wallich, M.D., F.L.S., &c. 



Although certain changes have taken place in the aspect of 

 the specimens of Amoeba villosa still met with in the remain- 

 ing portion of the Hampstead material in which they were 

 originally discovered, these neither involve the loss of any 

 essential characters, nor can they justly be regarded as any- 

 thing more than mere changes in degree. As now seen, the 

 individuals have become somewhat reduced in size; they con- 

 tain less fresh-looking organic food-particles; their movements 

 are more sluggish ; the nucleated corpuscles and sarcoblasts 

 are not so frequently met with ; the crystalloids, although not 

 less numerous, are smaller; the nucleus is shrunk somewhat, 

 but still retains its very marked membranous capsule; the con- 

 tractile vesicle performs its diastole and systole at longer inter- 

 vals ; and, lastly, the villi are not so densely studded over the 

 surface of the villous region. But inasmuch as these evidences 

 of impaired vitality are equally manifest in very recently pro- 

 cured specimens, it is probable that they are due to the opera- 

 tion of identical causes — namely, failure of proper nutriment 

 incidental on the season, or temporary stagnation, without ab- 

 solute drying-up, of the water in which they live. 



In the August Number of the 'Annals' (p. 124) I expressed 

 my doubts as to the " reproductive cells'' of Mr. Carter (assum- 

 ing these to be the same bodies to which I had given the name 

 of sarcoblasts) being the product of repeated binary division of 

 the nucleus, and I gave reasons for inclining to an opposite 

 conclusion. My late observations show that these doubts were 

 not unfounded ; for whilst I am able to confirm Mr. Carter's 

 statement regarding the recurrence of nuclear division up to a 

 certain limit, I still experience the same difficulty in reconciling 



Ann. ^ Mag. N. Hist. Ser. 3. Vol. xii. 22 



