THE CELLULAR BASIS 173 



of chromosomes in cleavage is abnormal the 

 larva shows abnormal characters (Boveri) ; 

 sex determination is associated with the distri- 

 bution of a particular chromosome to one-half 

 of the spermatozoa, and the fertilization of the 

 egg by one type or the other of spermatozoa 

 (Wilson) ; the linkage of certain characters 

 of Drosophila into four groups which corre- 

 spond with the four chromosomes of the sex- 

 cells of that animal indicates that the differen- 

 tial causes of these characters are located in 

 the chromosomes (Morgan). 



On the other hand it is objected by certain 

 investigators, notably by Child, Foot and Stro- 

 bell, that chromosomes are not the causes of 

 anything, but that they are the "results of 

 dynamic processes," "the expression rather 

 than the cause of cell activities." This objec- 

 tion seems to confuse the idea of natural cause 

 with that of final cause. Science knows noth- 

 ing of the latter; any natural cause is only a 

 link in the chain of cause and effect, it is itself 

 the result of antecedent causes and the cause 

 of subsequent results. Undoubtedly the 

 chromosomes are the results of antecedent pro- 



