September 30, 1910] 



SCIENCE 



431 



is mainly occupied with the results of experi- 

 ments. Further instances of this lack of dis- 

 crimination will appear in the consideration 

 of the various topics discussed. The bibli- 

 ographies are extensive, but the references to 

 them are comparatively few. The large 

 amount of recent work upon sex determina- 

 tion by cytologists and experimental breeders 

 receives but slight mention and, when referred 

 to, is apparently not correctly understood. 

 Professor Eusso promises, however, an early 

 consideration of this part of his subject and 

 it is to be hoped that he will then make some 

 effort to show the errors of those who find sex 

 independent of external conditions. In com- 

 menting upon the details of Professor Eusso's 

 investigations it will be convenient to ask cer- 

 tain questions and to examine the evidence 

 which he adduces in his replies to these. 



First it may be asked if there are two recog- 

 nizably distinct types of eggs in the rabbit 

 ovary. An answer to this question can hardly 

 be given justly from a mere inspection of the 

 evidence in the paper. The figures presented 

 are few and apparently indicate a morpholog- 

 ical difference between the eggs, but there is 

 no attempt made to determine the relative 

 numbers of these under normal conditions or 

 to show that there is a lessening of one type 

 to accompany the increase of the other under 

 the conditions of the experiment. It must 

 also be recalled that experienced investigators 

 like Heape^ not only fail to find two types of 

 normal eggs, but regard the supposedly male- 

 producing eggs of Eusso as those in process of 

 degeneration. It can at least be said that the 

 great importance attached to this part of his 

 work by the author would require his deter- 

 minations to be made more exact if they are 

 to be effective as an argument in the minds 

 of those familiar with ovarian histology. 



Also it may be asked, if there are two nor- 

 mal types of eggs, whether it is possible to 

 change one into the other by external influ- 

 ences. Eusso's theory requires that this be 

 done, but the evidence that he brings forward 

 in support of his contention that this has 



•Heape, W., Proc. Camhridge Phil Soc, Vol. 14, 

 1908, p. 609. 



been done is far from conclusive. Having 

 artificially nourished female rabbits with leci- 

 thin, he kills them and studies the ovaries and 

 reports that the proportion of fat containing 

 eggs has been greatly raised. Similarly 

 treated rabbits are bred and the proportion of 

 females is said to be much increased. It is, 

 therefore, concluded that one type of egg has 

 been changed into the other. In addition to 

 this evidence, which is all that there is to con- 

 nect form variation of eggs with sexual char- 

 acters, Eusso presents the results of experi- 

 ments upon fasting rabbits to show that the 

 fat within the eggs disappears completely, and 

 also those upon lecithin treated young to dem- 

 onstrate that the fat is here brought into 

 existence in eggs that normally do not acquire 

 it until much later. None of this evidence 

 proves that one kind of egg is changed into 

 the other, but only that the food material may 

 be increased or diminished by feeding and 

 starving. So far as the histological part of 

 the work is concerned, therefore, it may be 

 said that the evidence brought forward seems 

 to indicate that injections of lecithin may 

 affect the metabolism of the ovary and its 

 germ cells, but that there is no proof of the 

 view that such treatment is effective in trans- 

 forming one kind of egg into another. 



The question may next be asked: Does the 

 treatment of the maternal parent by the in- 

 jection of lecithin alter the proportion of the 

 sexes ? Eusso says very positively that it does 

 and that the proportion of females may be 

 raised from approximately 50 per cent, to a 

 very much higher one, even to 100 per cent, 

 in individual eases. Such results iAS these 

 seem unequivocal enough, but the same ex- 

 periments have been repeated by Basile ' and 

 by Punnett" and these investigators fail en- 

 tirely to substantiate the claims made by 

 Eusso for his methods. It is pointed out by 

 them and more recently by Castle* that 

 Eusso gave only selected results and failed 



= Basile, C, Atti Acad. Lined, Vol. 17, 1908. 



= Punnett, R. C, Proc. Camhridge Phil. Soc, 

 Vol. 15, 1909. 



* The Amcric^ii Naturalist, Vol. 44, No. 523, 

 1910. 



