1 88 KATHARINE FOOT AND E. C. STROBELL. 



conclusions. He says Morgan's results "bring strong support 

 to the view that the chromosomes are such bearers of unit- 

 factors, for the whole series of phenomena determined in Droso- 

 phila, complicated as they seem, become at once intelligible 

 under the assumption that certain factors necessary for the 

 production of the sex-limited characters are borne by the X 

 chromosome; and without this assumption they are wholly 

 mysterious" (pp. 420-1). 



As opposed to these definite expressions of faith in the causal 

 nature of the chromosomes, we may quote Child's latest repudi- 

 ation of all such hypotheses. "Let us take the case of the 

 chromosome, for example, which plays so important a part in 

 recent biological hypothesis. What is the chromosome? If it 

 is what many authors seem to believe, it is an autonomous being 

 endowed with something more than human intelligence. But if 

 we are not willing to believe this, then we must regard the 

 chromosome as an incident or result of dynamic processes in the 

 organism, like other morphological entities. If this is the 

 correct view, then it is nothing ultimate or fundamental. We 

 must analyze it into terms of the processes which have made it, 

 and in this analysis we shall sooner or later find nothing more or 

 less than the whole complex of processes which constitute the 

 organism. The organism makes the chromosomes, not the 

 chromosomes the organism" (pp. 33). 



Our cytological studies have caused us to sympathize with the 

 many investigators who have expressed skepticism of the 

 causal nature of the chromosomes. For several years we have 

 argued that the chromosomes in the forms we have studied show 

 too much variability, both in their morphological and physio- 

 logical expressions, to justify those theories which obviously 

 demand a rigid compliance to a definite mode of expression. 

 We demonstrated in 1905 that the form and relative size of the 

 chromosomes in Allohbophora fcetida are inconstant and in 

 every publication since that date we have demonstrated vari- 

 ability in the form, relative size and behavior of the chromo- 

 somes in every form we have studied, and we have consistently 

 argued that such variability attacks the very foundations upon 

 which the popular chromosome speculations of this decade have 

 been built. 



