PRESENT STATUS OF CHONDRIOSOME PROBLEM. 75 



in this connection: the behavior towards preserving reagents 

 and dyes; or better still, the evolution of a given cell-constituent, 

 as for instance in the seminal cells; or the continuity of a given 

 structure from the embryonic cell to the adult stage. If however 

 our objector means to say that it may be difficult in a given case 

 to decide whether or not a certain structure is a chondriosome, 

 then I heartily agree with him, but I fail to see therein a reason 

 for general scepticism. Rather it should prove a stimulus for 

 further investigation. It should not be forgotten that the chon- 

 driosomes are by no means the only structures that may be hard 

 to identify in certain instances. Indeed, sometimes we have great 

 difficulty in recognizing a nucleus. Take for example the con- 

 troversy on the so-called Blochman's nuclei in the egg of certain 

 insects, or (as a personal illustration) the divergence of opinion 

 between Retzius and myself as to what part of the spermatozoon 

 of dona is the nucleus. In this very field (spermiogenesis) the 

 same difficulty is met with constantly when we attempt to study 

 atypical forms. 



I come now to the second part of this address: what is still 

 to be done in the investigation of the chondriosomes? Since 

 brevity is essential, I shall limit myself to the consideration of 

 two questions, both of great importance i. e., the role played by 

 the chondriosomes in the process of differentiation and their role 

 in fertilization. Meves was the first to express the opinion that 

 the chondriosomes of the embryonic cell represent an indifferent 

 material, susceptible of various differentiations in the different 

 tissues. Since that time a number of papers supporting this 

 idea have been published, of which I shall only mention those on 

 the development of the collagenous fibrils (Meves), of neuro- 

 fibrils (Hoven) and of myofibrils (Duesberg). The same idea is 

 also and very strongly supported by a number of observations 

 concerning the processes of differentiation in vegetal cells. My 

 own observations on myofibrillogenesis have found confirmation 

 in different quarters and so far no specific criticism has been 

 expressed. On the other hand, the conclusions concerning the 

 chondriosomal origin of the neurofibrils and of the collagenous 

 fibrils have been criticized, respectively by Cowdry and M. R. 

 Lewis. I frankly admit that Cowdry 's arguments are worth 



