OF THE PEOTOZOA. EHIZOPODA. 233 



parts of the higher animals and plants, and the unicellular condition the 

 simplest form in the animal kingdom." The existence of an investing mem- 

 brane in the Rhizopoda he finally considers probable. 



The arguments here quoted from Kolliker's paper on Actinophrys, have been 

 examined by several later writers, and have had their defects pointed out. 

 Perty declares himself opposed to the cell-theory since Ehizopocla are want- 

 ing the essentials of the cell-nucleus and cell-wall ; and the hypothesis cannot 

 be applied to animals composed not of cells, but of an amorphous primitive 

 substance. 



M. Claparede attacks Kolliker's arguments in detail. The question raised, 

 whether the nucleus and membrane may not disappear in the course of 

 growth, he answers by another queiy — " \Ye may conceive the possibility of 

 this ; but where do we find any proof of it ? " — and proceeds to remark his own 

 failure, and that of Ehrenberg and of most others, to discover a nucleus, even 

 in very small animals, and after treating them with dilute acetic acid. " The 

 supposition, that Actinoplirys and other Ehizopoda pass through a previous 

 cellular condition, has consequently no foundation in fact." He cannot agree 

 with Kolliker, that of the three parts of a cell — the nucleus, membrane, and 

 contents — two " may be deficient, — that for example, we may attribute the 

 signification of a cell to the contents remaining alone and contained in 

 nothing .... If, therefore, with Kolliker, we regard the Ehizopoda as a class 

 of unicellular animals, the organisms which it includes will be principally 

 distinguished by their having nothing to do with cells, as they consist of a 

 shapeless mass of a stinictureless homogeneous substance." 



M. Claparede next subjects to examination the argument for the cell-nature 

 of Ehizopoda deduced fi^om analogy with Ciliated Protozoa, which Kolliker 

 takes for granted to be unicellular organisms. This assumption, and conse- 

 quently the analogy dependent on it, are shown to be erroneous ; and then 

 the wiiter goes on to say that, ''.even if we admitted that Actlnophrys was 

 the equivalent of a cell, it would still not be unicellular, inasmuch as an 

 endogenous cell-production has taken place in it. The contractile vesicle is 

 nothing but a cell" invested by a membrane ; and this being the case, the 

 existence of such a membrane in other Ciliated Protozoa becomes all the more 

 probable. " Kolliker himself supposes that the contractile vesicle, when pre- 

 sent, is the equivalent of a cell-membrane ; and with the proof of the exist- 

 ence of such (an endogenous) formation in Actinophrys, his hy^Dothesis of the 

 unicellular constitution of the animal consequently falls to the ground." 

 Leuckart has also briefly argued against the cell-theory of Ehizopoda ; but 

 as no novel views are taken of the question, we shall not quote his remarks. 

 Our own opinion is, that to insist upon the unicellular nature of Ehizopoda 

 and of other Infusoria is to limit the operations of natiu^e, in the manifesta- 

 tion of animal life, to one sort of mechanism, as though life could not be 

 exhibited except by an organic substance enveloped by a membrane and 

 enclosing a nucleus. Eeasoning by analogy should teach us differently ; for 

 everywhere in the animal series do we see ty^Dcs or grades of organization 

 progressively developed from theii^ simplest to a more or less complicated 

 degree, as if nature would show us by how many different plans she can 

 attain similar and equally beneficial results. And are not the Ehizopoda an 

 illustration of this fact, an example of the establishment of independent 

 animality in primordial animal matter, and, as in the case of the multilocular 

 Polythalamia, of the possible extent of development tliis simple type may 

 undergo without the separation or addition of any other definite structural 

 element ? 



If Schneider's researches be confirmed, we must admit several Ehizopoda 



