LITERATURE 3^q 



on from cell to cell, whether by cell-division or by fertilization ; and 

 that it may be a primary factor in the constructive processes of the 

 nucleus and through these be indirectly concerned with those of the 

 cytoplasm. 



The role of the nucleus in constructive metabolism is intimately 

 related with its role in morphological synthesis, and thus in inheri- 

 tance ; for the recurrence of similar morphological characters must in 

 the last analysis be due to the recurrence of corresponding forms of 

 metabohc action of which they are the outward expression. That the 

 nucleus is in fact a primary factor in morphological as well as chemi- 

 cal synthesis is demonstrated by experiments on unicellular plants and 

 animals, which prove that the power of regenerating lost parts disap- 

 pears with its removal, though the enucleated fragment may continue 

 to live and move for a considerable period. That the nuclear sub- 

 stance, and especially the chromatin, is a leading factor in inheritance 

 is powerfully supported by the facts of maturation, fertilization, and 

 cell-division. In maturation the germ-nuclei are by an elaborate 

 process prepared for the subsequent union of equivalent chromatic 

 elements from the two sexes. By fertilization these elements are 

 brought together, and by mitotic division distributed with exact equal- 

 ity to the embryonic cells. The result, which is especially striking in 

 the case of hybrid-fertilization, proves that the spermatozoon is as 

 potent in inheritance as the ovum, though the latter contributes an 

 amount of cytoplasm which is but an infinitesimal fraction of that 

 supplied by the ovum. 



It remains to be seen whether the chromatin can actually be re- 

 garded as the idioplasm or physical basis of inheritance, as maintained 

 by Hertwig and Strasburger. Verworn has justly urged that the 

 nucleus cannot be regarded as the sole vehicle of inheritance, since 

 the cooperation of both nucleus and cytoplasm is essential to com- 

 plete cell-life; and, as will be shown in Chapter IX., the cytoplasmic 

 organization plays an important role in shaping the course of devel- 

 opment. Considered in all their bearings, however, the facts seem 

 to accord best with the hypothesis that the cytoplasmic organization 

 is itself determined, in the last analysis, by the nucleus ; ^ and the 

 principle for which Hertwig and Strasburger contended is thus sus- 

 tained. 



LITERATURE. VII 



Bernard, Claude. — Lepons sur les Phenomenes de la \'ie : ist ed. 1878: 2d ed. 



1885. Paris. 

 Chittenden, R. H. — Some Recent Chemico-phvsiological Discoveries regarding tlie 



Cell : Am. Nat.. XXVIIL, Feb., 1894. 



1 C/p. 431- 



