448 Dr. G. C. Wallich on the Distinctive Characters, Habits, 



XLVIII. — Further Observations on the Distinctive Characters, 

 Habits, and Reproductive Phenomena of the Amoeban Rhizo- 

 pods. By G. C. Wallich, M.D., F.L.S., &c. 



[Plate VIII.] 



In order to show the fallacy of regarding mere external modifi- 

 cations of the sarcode-substance as indicative of specific indi- 

 viduality amongst the Amoeban Rhizopods, attention was di- 

 rected in my previous papers to the intimate relation existing 

 between such modifications and the varying nature of the con- 

 ditions by which most of these lower forms of animal life are 

 surrounded. I have now to offer the following observations in 

 support of this view. 



Whilst describing the singular phase in the history of Amoeba 

 whereby, in common with many of the more highly organized 

 Protozoa, it survives the contingencies to which it is exposed 

 through the drying up or deterioration of the medium it inha- 

 bits, I mentioned having detected, amongst certain confervoid 

 matter, an abundant brood of this organism, and that in it 

 were embodied the collective characters of numerous forms whose 

 specific distinctness had been based almost entirely on the cha- 

 racters of their pseudopodia. The specimens alluded to, in 

 conjunction with some obtained from other sources, afford ex- 

 cellent illustrations of the incidental nature of these varieties, 

 and seem to furnish conclusive evidence not only that the figure 

 assumed by the pseudopodia is subject to such a degree of 

 variation as to become valueless as a distinction between the 

 Amoeban species, but that the extent of the variation is so great 

 as even to invalidate the boundary-line between Amoeba and 

 Actinophrys, in so far as it depends on the character in question. 



This view may, at first sight, appear overstrained ; for I 

 confess that, in my own case, nothing short of the constant 

 repetition of the appearances through an extended series of 

 specimens could have induced me to entertain it. It is true, 

 moreover, that the transition from the form of pseudopodium 

 said to be typical of Amoeba to that held to be typical of Acti- 

 nophrys had not previously been noticed by me with anything 

 like the same distinctness. But, in the material under notice, 

 the specimens exhibiting the transitionary characters were so 

 numerous, the alternation of the characters so frequent, and the 

 type assumed so well sustained, that, should the case be deemed 

 exceptional, it ought certainly to be regarded as one of those 

 very important exceptions that disturb the established rule. 

 And hence, admitting the accuracy of the facts recorded, namely 

 that, under any circumstances whatever, a true Amoeba possesses 

 the power of projecting from its surface the tapering and pointed 



