CANNIBALISM IN AMOEBA 671 



Protozoa. Other stains used were Heidenhain's watery iron 

 haematoxylin and Delafield's haematoxylin. A counterstain 

 was not used, since it is quite unnecessary after these stains 

 and, in the opinion of the writer, tends to obscure, rather than 

 to improve, the results. Both Bausch and Lomh and Zeiss 

 microscopes were used, the ordinary high power dry lens being 

 sufficient for most of the observations on the living objects ; 

 but, when higher magnification was needed, a Zeiss apochro- 

 matic oil immersion was used. 



2. Characters of Amoeba vespertilio. 



Considerable difficulty was experienced in the identification 

 of the amoebae present in the cultures. It is not my intention 

 to enter here into this vexed question ; but it is necessary to 

 record the opinion that species of amoebae estabhshed upon 

 descriptions of their external characters alone, without a pro- 

 longed study of them under all conditions and a knowledge 

 of their nuclear apparatus and hfe-history, supported by the 

 evidence of stained preparations, must be regarded as pro- 

 visional only. 



Until such detailed knowledge is available, however, the 

 existing data must be utilized ; and, when I say that the 

 amoeba which forms the subject of this paper corresponds with 

 that described by Dofiein (9) and Penard (21) as Amoeba 

 vespertilio, it should be understood that I do not neces- 

 sarily regard Amoeba vespertilio as a true species. 



The account and figures of this amoeba given by Doflein (9) 

 are so excehent, and my own observations upon it confirm 

 his so exactly, that it is unnecessary for me to give here more 

 than a summary of its distinctive characters. 



Amoeba vespertilio is a small amoeba, showing a well- 

 marked contrast between clear ectoplasm and granular endo- 

 plasm, and is, when healthy, very active. Its pseudopodia 

 are typically branched, with pointed ends, and are composed 

 mostly of ectoplasm. When the amoeba is creeping along 

 a substratum, it assumes a very characteristic shape, resem- 

 bling that of a bat's wing or of a duck's foot. The form is, 



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