472 HeiT R. S. Bergh on the 



typical larvEe of B, and consequently was '' devoid of maternal 

 participation." This experiment of Boveri's is ingeniously 

 carried out and very instructive ; but it in no way proves 

 what the author himself* and many other investigators 

 maintain. It demonstrates that the yolk of the ovum (not 

 merely the nutritive, but also the formative yolk — apart from 

 the centrosoma) is of no importance for the transmission of 

 parental characters, and consequently substantiates Nageli's 

 doctrine of the difference between idioplasmic substances and 

 those consisting of nutritive plasma. But the experiment in 

 no way proves that the nucleus is the sole vehicle of heredity; 

 for in his memoir on this subject Boveri makes no mention of 

 the centrosomata, which is the more astonishing since he 

 belongs to the investigators to whom credit is due for the 

 recognition of the importance of these bodies. But now it is 

 clear, since the division of the cells took place in the normal 

 course, and a typical larva was developed, that centrosomata 

 were present in the fertilized egg-cell and in the segmentation 

 cells. Whence did these arise ? It is well known that the 

 centrosomata, in cases where they have been shown to exist 

 in the resting-cell, are always situated in the immediate 

 neighbourhood of the nucleus ; and it is therefore in the 

 highest degree probable that the centrosoma of the ovum was 

 eliminated with the nucleus by the process of shaking, and 

 that the new centrosomata, wliich displayed their activity in 

 the fission of the egg-cell, developed from the spermatozoon 

 which penetrated the latter. Fol's observations in particular, 

 which we shall discuss directly, render this explanation very 

 probable, and indeed they show that it is really the only 

 possible one. In order to prove the theory that the heredi- 

 tary characters are situated in the nucleus, a corresponding- 

 experiment would have to be carried out in the following 

 manner : — The ovum of a species (A) must be deprived of 

 its nucleus, but must retain its centrosoma. Then if, after 

 fertilization with the sperm of another species (B), a larva 

 developed which agreed in all its characters with the typical 



* At the commencement of his communication Boveri writes : — 

 " Although the proposition, that the substances of the cell which deter- 

 mine and transmit character are exclusively contained in the nucleus, is 

 expressed in many .places no longer merelj as a highly probable hypo- 

 thesis, but already as a fact, it would nevertheless be easy to show that 

 it can neither be proved by the phenomena of the fertilization of the 

 ovum, with which we are acquainted, nor by the experiments which have 

 liitherto been instituted upon the role of the nucleus in the Protozoa." 

 And after communicating his experiment he then says : — "Thereby 

 also the proposition, that the nucleus is the sole vehicle of lieredity, is 

 proved." 



