THE CYTOPLASM IN HEREDITY 37 



Godlewski sums up his results as follows : " So, however 

 cautiously these experimental results are considered, we 

 arrive at least at this : up to the gastrula stage maternal 

 characters may occur without the presence of the maternal 

 nucleus." l 



Meves in criticising these experiments comes to the 

 conclusion that the results are sufficient to controvert the 

 theory that the nucleus is the sole bearer of those entities 

 which ensure the transmission of hereditary characters. 2 



Boveri's later views seem also to tend somewhat towards 

 a similar conclusion. 3 He points out that it is obvious that 

 those factors which so work together in the egg as to give 

 rise to an individual of the same species as the parents, 

 must lie partly, at any rate, in the cytoplasm. There is, 

 however, a great difficulty in the enormous preponderance 

 of cytoplasmic material in the egg as compared with that 

 in the sperm, and in the fact that nevertheless the new 

 individual is as much like the father as the mother. Here, 

 according to Boveri, the cytoplasm of the egg is not con- 

 cerned. The transmission of specific characters from the 

 parents to the offspring depends exclusively upon the 

 chromosomes supplied by the egg and the sperm. Boveri 

 comes to the conclusion that in development there are 

 two distinct periods. In the first, the cytoplasm of the 

 egg is directive, and only certain properties of the chromo- 

 somes come into action. In the second period, the chromo- 

 somes begin to exercise their full influence. According to 

 this, the first developmental period is decided by the con- 

 stitution of the cytoplasm, and Meves considers this the 

 more probable because in some hybridisation experiments 

 the characters appearing during this period are purely 

 maternal. Boveri considers that his theory is brought into 

 line with the experiments of Godlewski, because in the 

 enucleated fragments of the Echinus eggs fertilised with 



1 Godlewski, 1906, op. cit., p. 35. 



a Meves, 1908, op. cit., p. 35. 



3 Boveri, Th., Zellen-Studien, Heft 6, 1907. 



