204 PROTOPLASM 



are expressed by Fr. Scliwarz (1884) upon the reticular 

 structure of protoplasm. 



What his conception of protoplasm really is, does not 

 appear to me sufficiently clear from his extensive treatise. 

 He declares (p. 130) that all authors are agreed upon the 

 point " that protoplasm consists of solid and fluid parts," 

 from which it is to be concluded that he, in like manner, 

 supports this view. On the other hand, however, he speaks 

 also of the " semi-fluid " nature of protoplasm. Now, since 

 he denies in the most definite manner that the firm sub- 

 stance of protoplasm appears in the form of a framework, 

 he comes to the conclusion that protoplasm must be a 

 " mixture, which in external appearance is homogeneous, but 

 seems nevertheless to admit the possibility of the single 

 substances being variously distributed" (p. 130). On p. 

 125, also, it is said with reference to the investigations of 

 Eeinke and Eodewald, that " there might be a homogeneous 

 mixture, of the framework and the enchylema," which was 

 not to be separated by the action of centrifugal force. But 

 what this " homogeneous mixture " may be in reality is not 

 clear to me. If protoplasm is supposed to consist of solid 

 and fluid parts, they could only be indistinguishable if they 

 possessed exactly the same power of refraction. But since 

 it is inconceivable that such a thing should occur universally, 

 it is incomprehensible to me how Schwarz arrives at the 

 statement (p. 130) that it is never possible to convince 

 oneself of the presence of a framework in living protoplasm 

 an assertion which was the more unjustifiable because 

 numerous investigators even before Schwarz had convinced 

 themselves of its existence. Unfortunately Scliwarz, while 

 talking about protoplasm in quite a general manner, has 

 by no means taken into consideration the numerous observa- 

 tions on the zoological side. He appeals, indeed, to Flemming, 

 without, however, appreciating or paying more special atten- 

 tion to what is communicated by him. 



What he himself has described in the way of filamentous 

 protoplasmic structures in vegetable cells were, in my 

 opinion, as a rule nothing of the sort, but merely networks 

 of minute trabecula 3 of protoplasm which traverse the cell 



