356 cook 



accidental, but are a biological necessity in the elaboration of 

 the framework of symbasic descent which sustains the organic 

 vigor of the species. 



In cytology, no less than in the more general fields of study, 

 it is the physiological values which need first to be ascertained? 

 before the morphological considerations can be correctly appre- 

 ciated. Germ-cells can indeed be viewed as mechanisms of 

 descent, but speculations regarding them should not be made 

 the basis of evolutionary thought nor the test of orthodoxy, to 

 the exclusion of more definite and concrete indications of the 

 nature of evolutionary processes. 



The kinetic theory finds significance and confirmation in the 

 now rapidly accumulating indications of an extensive series of 

 fusions between the individual granules of chromatin, which 

 previous cytological interpretations, based on static views of 

 evolution, have denied. From the kinetic point of view the 

 fusions of the chromatin are an important and altogether ac- 

 cordant part of the whole system of evolution ; they are the ac- 

 tual knots and junctions of the fabric of descent. Static theories 

 of cellular determinants, on the other hand, can see in these 

 evidences of fusion only an elaborate deception, an unnecessary 

 complexity of the process of reproduction, just as it was for- 

 merly held that sexual reproduction itself stood in the way of 

 evolution, because it interfered with the subdivision of species 

 and the isolation of new variations. 



The traditional concept of heredity, the ideal of uniformity in 

 descent, has furnished the basis of all preceding doctrines of 

 evolution. Conditions of isolation or of restricted descent have 

 accordingly been considered typical for evolution, because it was 

 only in narrow bred groups that the ideal of uniformity could 

 be approximated in nature. The kinetic theory breaks with all 

 these traditions, and seeks to substitute for the abstract concep- 

 tion of a uniform, definite or mechanical heredity, a recognition 

 of the concrete fact of normal diversity, inside the species. 



6. THE CONSTITUTION OF SPECIES. 



Astronomy is reckoned as queen among the sciences because 

 it has demonstrated that definite and orderly relations exist 



