8 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Such facts have led many workers to look to the meta- 

 bolism and not to the chromosomes as the basis of sex 

 determination ; but the cytological facts brought to light during 

 the last few years have been so overwhelmingly in favour 

 of the X chromosome theory, that suggestions which centre 

 round the metabolism alone, have not carried any real 

 conviction. 



It seems possible, however, that sex may be a result of 

 the type of metabolism and still be in harmony with the 

 observed distribution of chromosomes. 



I wish to suggest tentatively, that sex may be the expression 

 of a fundamental rhythmical reaction of protoplasm itself, giving 

 an alternation between two types of metabolism characteristic 

 of maleness and femaleness respectively.* A great number 

 of natural phenomena have been found to be oscillatory, 20 

 particularly bio-chemical reactions, and I suggest that sex 

 may be due to another of the many rhythms found in living 

 matter, and that, left to run its course apart from any mixing 

 at fertilization, protoplasm would tend to give an alternation 

 between maleness and femaleness. When mixing does occur, 

 as at fertilization, the " strongest " germ-cell would be expected 

 to determine the type of metabolism of the zygote, the 

 " strong " egg giving a male, the " strong " sperm a female. 



* This idea, of course, involves the supposition that the metabolism 

 of the two sexes is fundamentally different, and this, as a fact universally 

 applicable, is by no means proven ; unless the production of anabolic germ 

 cells by the female and katabolic germ cells by the male be accepted as 

 proof. There are, however, other indications that in the higher animals 

 at least, the sexes are characterised by different types of metabolism. In 

 man, i 6 for example, the blood has a higher specific gravity, more red blood 

 corpuscles, and a higher percentage of haemoglobin than in women : men 

 retain much more calcium than women : the basal metabolism" of men 

 is about 6 per cent, higher than that of women. Amongst insects, too, 

 sortie^ caterpillars have green blood in the females, and yellow or colourless 

 blood in the males. All these differences may, of course, be secondary, 

 but in the hermit crab, Geoffrey Smiths has shown that a change in meta- 

 bolism, caused by the parasite Sacculina, brings about a change in the 

 sex of the individual even to the extent of a change from sperm production 

 to egg production. This strongly suggests that it is the type of metabolism 

 which determines the sex, and not the sex which determines the type of 

 metabolism. 



