Makch 8, 1907] 



SCIENCE 



375 



has the greater vitality. He concludes: 

 "This indicates that there is a physiolog- 

 ical difference between Paramoeciiim gam- 

 etes analogous to that existing between egg 

 and spermatozoon." 



It would seem that the view that species 

 have periodic phases of inefficiency, cor- 

 rected by fertilization, is well founded. 

 But it is difficult to see how the union of 

 two like inefficiencies may restore efficient 

 functioning. I have much sympathy with 

 Weismann's strictures on the hypothesis 

 that the union of two senescent beings may 

 produce one rejuvenated being. But if we 

 conceive fertilization as always selective, 

 i. e., between physiologically differentiated 

 gametes, then the fertilization-need must 

 be different on the two sides ; and this may 

 be conceived in one of two ways: either 

 the gametes represent plus and minus devi- 

 ations, respectively, from the physiological 

 mean, in which event fertilization might be 

 supposed to be a reciprocal process ; or one 

 gamete may be supposed to act as stimulus 

 and the other as the element stimulated, in 

 which event fertilization would not be re- 

 ciprocal, but one-sided. Now, fertilization 

 in ciliate infusoria has always been sup- 

 posed to be a reciprocal process, and the 

 morphological phenomena are all in favor 

 of this point of view; but Calkins 's results 

 indicate that only one of the ex-conjugants 

 is benefited; the fertilization is one-sided 

 physiologically. 



In either event, union in the zygote 

 would restore the physiological mean or 

 condition of equilibrium, and the question 

 would arise, how the differentiated condi- 

 tions are subsequently produced. Nothing 

 definite can be said about this at present; 

 but it is obvious that the protoplasm does 

 tend inevitably away from the condition of 

 equilibrium towards one or the other dif- 

 ferentiated condition; the direction of the 

 tendency appears to be dependent on 

 stimuli. 



The objection may be raised that in some 

 animals sex is certainly determined in the 

 ovum at the time of fertilization, whereas, 

 according to the point of view presented, 

 fertilization is supposed to balance the 

 physiologically differentiated conditions on 

 which sex depends. Sexual determinate- 

 ness of the fertilized ovum may, however, 

 be interpreted to mean only that the sex- 

 determining factors, primitively external, 

 have been replaced by internal conditions 

 in these cases. It is certainly not an illog- 

 ical position that physiological neutrality 

 in regard to sex may coexist along Avith 

 internal conditions that absolutely restrict 

 sexual differentiation to one direction. 



In his thoughtful and suggestive paper 

 on 'The Phenomena of Sex Differentia- 

 tion,' Watase comes to the conclusion that 



The organism is either a male or a female, not 

 by the difference of primary sexual characters 

 alone, but by the difference which saturates the 

 whole of its entire structure. Such a difference 

 is, liowever, neither absolute nor permanent. It is 

 a temporary differentiation of protoplasm into one 

 of two different directions, and sooner or later 

 comes back to the original neutral or non-sexual 

 state from which it started, thus manifesting the 

 phenomenon characteristic of all protoplasmic ir- 

 ritability. 



His point of view is instructive ; there is 

 a sexually indifferent stage of the organ- 

 ism corresponding to the period of union 

 of the germ-nitclei ; sexual differentiation is 

 a phenomenon of irritability or response to 

 stimulus, which lasts throughout the life 

 history of the growing organism; 'and the 

 recurrence of the irritable condition cor- 

 responds to the production of the unicel- 

 lular embryo.' Sex differentiation is thus 

 one of the phenomena of irritability, and 

 it differs from other phenomena of this 

 class only in the slowness of its rhythm. 



"VVatase's conclusions M^ere based on the 

 observations of Auerbach, himself and 

 others, that the staining reactions of the 

 egg and sperm nucleus are entirely differ- 



