38 HEREDITARY CHARACTERS 



the sperm of a Crinoid, development only reached the 

 gastmla stage. According to Boveri's theory, this stage 

 is the utmost which could be reached in these experiments. 

 They certainly have been carried no further up to the 

 present. 



Oscar Hertwig has expressed very similar views. 1 



Meves's idea is that "the unfertilised egg builds up 

 plasma substances during the long maturation periods, 

 which, even if they are not ' organ-bildende,' are yet cer- 

 tainly necessary to the formation of the particular organs 

 later on. These different forms of plasma (cytoplasm) are 

 localised in a definite manner in the contents of the egg." 2 

 Godlewski says: "But at any rate these experiments show 

 that the organ-forming substances (Anlagesubstanzen), or 

 whatever else they may be called, cannot be regarded, as 

 they generally are, as being derived entirely from the 

 nucleus. The cytoplasm which the sperm brings into the 

 egg, small as it is, cannot be disregarded." 3 



Morgan showed that enucleated fragments of Echinoderm 

 eggs fertilised with sperms, developed, but that the cells of 

 the embryos only exhibited half the normal number of 

 chromosomes. This suggests that all the nuclear contents 

 are not necessary. 4 



These experiments and observations upon fertilisation 

 and development have led some biologists to regard the 

 cytoplasm as a bearer of hereditary qualities conjointly with 

 the nucleus. There is another and a somewhat different 

 view put forward by Verworn, which also attributed a share 

 in the transmission of the hereditary qualities to the cyto- 

 plasm. 5 Verworn, by cutting certain unicellular animals 

 into small pieces, showed that neither nucleus nor cytoplasm 



1 Hertwig, 0., " Allgemeine Biologie, Zweite Auflage des Lehrbuchs, " Die 

 Zelle und die Gewebe, 1906. 



2 Meves, op. cit., p. 35. 



3 Godlewski, op. cit., p. 35. 

 * Morgan, op. cit., p. 30. 



s Verworn, M., "Die physiologische Bedeutung des Zellkems," Archiv fur 

 die gesammte Physiologic, ii., 1891. 



