tup: determination of sex. ^^ 



the male element when fertilisation occurs, the embryonic 

 nutrition, and even the larval environment in some cases, 

 these and yet other factors have all to be considered. 



Some observations by Laulanie as to the embryonic organs are of 

 interest in this connection. He distinguishes both in birds and mammals 

 three stages in the individual development of the reproductive organs. 

 These he calls (i) Germiparity, (2) Hermaphroditism, (3) Differentiated 

 Unisexuality ; and regards them as parallel to the stages of historic evolu- 

 tion. Even for the first stage, however, when the elements are still very 

 primitive, he would not allow the accuracy of the terms neutrality or 

 indifference. The elements in both sexes are almost similar, but yet their 

 future fate has been decided. 



Sutton has also emphasised his conviction, that in the individual 

 development a state of embryonic hermaphroditism obtains, and main- 

 tains that one set of elements predominates over the other in the establish- 

 ment of the normal unisexual state. Ploss and others take up a similar position 

 in regard to an early hermaphrodite state. It can only be concluded, that 

 the higher the organism is in the series the earlier is its sexual fate sealed ; 

 and that it is only in lower vertebrates, and among backboneless animals, 

 that we can speak of prolonged neutrality of sex, or embryonic hermaphro- 

 ditism. 



§ 2. Ansivers to the Question: What Deter/nines Sex? — To 

 the question what settles whether an organism shall develop 

 into a male or into a female, many and varied answers have 

 been given. At the beginning of the last century, the theories 

 of sex were estimated at so many as five hundred, and they have 

 gone on increasing. It is evident that even an enumeration of 

 these is not possible, nor is it indeed desirable. As in so 

 many other cases, our ideas respecting the determination of sex 

 have been looked at in three different ways. For the theologian, 

 it was enough to say that "God made male and female." In 

 the period of academic metaphysics, still so far from ended, it 

 was natural to refer to "inherent properties of maleness and 

 femaleness;" and it is still a popular "explanation" to invoke 

 undefined " natural tendencies " to account for the production 

 of males or females. This mode of treatment, it need not be 

 said, is being abandoned by biologists. It is recognised that 

 the problem is one for scientific analysis ; thus the constitu- 

 tion, age, nutrition, and environment of the parents must be 

 especially considered. These investigations, which are mainly 

 restricted to observation and statistics, will be first noticed ; the 

 more experimental researches, and the general conclusions, will 

 be discussed in the next chapter. That the final physiological ex- 

 planation is, and must be, in terms of protoplasmic metabolism, 

 we must again, however, remind the reader (see p. 27, note). 



c 



