354 riddle: control of sex ratio 



tissue — to a higher metabolism; supporting this point of view is 

 the observed fact that "differentiation" is much hastened in this 

 male individual as compared with the otherwise wholly similar 

 larva that is destined to become a female. 



What it has been our privilege and opportunity to present is 

 in itself but an outline or summary of result obtained in the 

 modification and control of sex, and of the conclusions that 

 seem to follow from these results. In a closing statement, there- 

 fore, we wish only to direct attention to some consequences of 

 the new knowledge of sex. As a foreword to this statement, 

 however, we would note that not only do the widely different 

 kinds of fact to which we have made reference directly support 

 the view of the basis of sex here presented, but that nothing 

 known of the sex-chromosomes is necessarily opposed to this view 

 although an abundance of the data here presented sharply op- 

 pose the conception that the sex-chromosomes are a cause of sex, 

 or that they are even a necessary associated phenomenon. We 

 may conceive that sexually differentiated organisms, from the 

 first, have had the problem of producing germs pitched at two 

 different metabolic levels; and if two sharply opposed sexes are 

 to result from these two kinds of germs then the two metabolic 

 levels must be measurably distinct. This task of producing and 

 maintaining two kinds of cells pitched at two different levels 

 ultimately falls upon cells, and these have, sometimes at least, 

 produced two different chromosome complexes in connection with 

 or in accomodation to the establishment of these two metabolic 

 levels. Eut, as we have seen, the requisite metabolic level of 

 the germ may be established in the absence of the appropri- 

 ate chromosome complex, and the sex of the offspring made to 

 correspond with the acquired grade or level of metabolism. 



With these facts concerning the functional basis of sex in 

 mind, and reverting to our first quotation from Doncaster, 

 how little wonder that sex (despite its seeming "lack of func- 

 tion" is "nearly universally distributed," almost coequal with 

 "the fundamental attributes of living matter, irritability, as- 

 similation and growth?" Since some grade of metabolism is of 

 necessity universally present in living matter the basis for two 



