672 LECTURE XXIX. 



in the course of time the cells would lose to some extent the ability of trans- 

 forming rapidly the substances which are brought to them. At all events, 

 this is the only way in which the metabolism of more highly organized 

 beings could be affected. 



It is almost generally assumed that in the inheritance of certain proper- 

 ties the nucleus of the cell plays a particularly important part, and in fact 

 it is usually assumed that it alone is able to transmit the characteristics of 

 the parents. This is certainly not justifiable, for although the protoplasm 

 represents an apparently homogeneous mass, which is but slightly differ- 

 entiated and excites but little the interest of the histologist, it is not at all 

 apparent why, with its infinitely complicated composition, it should not be 

 capable of at least taking part in the processes named. In this direction the 

 following experiment of Godlewski 1 is interesting. He fertilized nucleus- 

 free fragments of Echinus eggs with spermatozoa of Antedon rosacea. It 

 was found possible in some cases to effect a development. Even these 

 nucleus-free pieces did not develop to be of the Antedon type. In order 

 to understand this experiment better, we should recall the investigations 

 of Loeb, 2 which we have previously mentioned, who succeeded in a great 

 number of cases in bringing eggs to spontaneous segmentation by the 

 action of certain salts in definite concentrations. Of great interest is his 

 discovery that under certain definite conditions the egg of a definite species, 

 e.g., that of a star-fish, could be fertilized by the spermatozoa of an entirely 

 different nature. We shall not go into the significance of these discoveries 

 any more deeply, but will briefly consider the outlook which Loeb himself 

 obtained from his experiments. He believes it is not at all improbable 

 that the greater part of the many different forms of life, particularly those 

 of deep sea, may have resulted from conditions which are not at all unlike 

 those of his experiments. It is indeed conceivable that in the course of 

 time the composition of the sea-water in certain localities may change so 

 that the conditions for the fertilization of one species are replaced by those 

 corresponding to a different one. We mention these experiments merely 

 to illustrate in what widely different ways biology seeks to penetrate the 

 mystery of life. To be sure, we are not justified in considering the inter- 

 esting results of Loeb's experiments as by any means solving the problem of 

 egg development, or even in hoping that by such a way we shall obtain an 

 insight into the laws of heredity. Loeb's experiments merely show that it 

 is possible, by changing the concentration of a salt solution in which the 

 unfertilized egg is placed, to bring about cell-division. They do not tell 

 us anything at all about the causes of cell-multiplication, and the reason 



1 Anzeigen der Akad. Wissensch. Krakau, 1905, 501. 



3 University of California Publications, 1, No. 1, p. 1 (1903) ; 1, 39 (1903) ; 1, 83 (1904); 

 2, 5 (1904). Pfliiger's Arch. 99, 323 (1903); ibid. 104, 325 (1904). Cf. Emil Abder- 

 halden: Arch. Rassen- und Gesellschaftsbiologie, 1, 656 (1904). 



