76 J. DUESBERG. 



being very carefully considered, but I should perhaps be allowed 

 at the same time to venture the question whether there is really 

 such a problem as the origin of neurofibrils; in other words, 

 whether the neurofibrils really exist in the living cell. As to the 

 fibrils of the connective tissue, a detailed criticism of M. R. 

 Lewis's paper is out of place here, but I want however to point 

 out that little effort has been made by that author to demonstrate 

 that the fibrils appearing in her tissue-cultures are collagenous 

 fibrils. Yet, I gather from Baitsell's observations that great 

 care should be taken in interpreting such fibrillar structures. 

 Personnally, I have not found in my recent investigations on 

 development, normal and regenerative, any reason for changing 

 my mind. I can clearly see however, how interesting it would 

 be to apply the experimental method to the solution of these 

 problems: experiments on regeneration of tissues, on centrifuged 

 eggs, on the behavior of cells under abnormal and pathological 

 conditions and under the influence of poisonous substances, etc., 

 a field which so far has been explored very little. 



The second question I want to consider is this: are the chon- 

 driosomes an idioplasmic substance? This opinion was first 

 expressed by Benda. It found strong support in Meves's dis- 

 covery of chondriosom.es in all embryonic cells and later in that 

 author's description of the behavior of the male chondriosomes 

 in Ascaris during fertilization. The question is so important 

 that it should be considered with greatest care and at some length. 



At the basis of the hypothesis of the idioplasmic nature of the 

 chondriosomes is the idea in which the protoplasm plays a role 

 in the transmission of hereditary characteristics. This opinion 

 has always been that of a number of biologists, although a 

 minority, and it has been supported by experimental researches, 

 namely by the well-known experiments made by Godlewsky. 

 The question then arises: what part of the spermatozoon repre- 

 sents the protoplasmic idioplasm? It cannot be the axile fila- 

 ment, which is not constant and is obviously an organ of motility; 

 it cannot be the headcap, nor the acrosome, since these are also 

 inconstant, in some cases (marsupials) only transitory parts of 

 the spermatozoon ; nor do I see that any argument can be brought 

 forth in favor of the idioplasmic nature of the centrioles, or of 



