272 BIOLOGY OF THE PROTOZOA 



garinida and in Ooccidiomorpha an asexual reproductive cycle 

 intervenes between the sporozoite and the gamont and the same is 

 true in the Foraminifera. In Infusoria, as Maupas long since 

 demonstrated, fertilization is possible only after a period of vege- 

 tative metabolism and reproduction. Sexual maturity in general 

 therefore, like other conditions of protoplasm, may well be inter- 

 preted as evidence of specific differentiations of the protoplasmic 

 organization. 



Few problems in biology have attracted more attention than 

 those associated with sex, and attempts to interpret the phenom- 

 enon have been as varied as they are sometimes ingenuous. The 

 very definition varies with different interpreters, the usual defini- 

 tion involving association of the concept sex with peculiarities of 

 structure and function which enable an observer to distinguish 

 males from females. Others regard sex as evidence of a fundamental 

 difference in protoplasm, one type giving rise to males, another 

 type to females as in Weininger's arrhenoplasm (male-producing) 

 and thelyplasm (female-producing). Or the differences of sex, 

 according to Minot (1S82) and Schaudinn (1904), are due to specific 

 types of chromatin both of which are present in all individuals 

 derived from a fertilized cell, but male chromatin predominating 

 in males, female chromatin in females. Still others interpret sex 

 differences as originating through metabolic activities, segregation 

 of protoplasm thus differentiated, and distribution by inequalities 

 in division of the cell as Biitschli first suggested. 



Not only somatic differentiations with their specific functions, 

 but products of such differentiation in the form of gametes together 

 with the causes which bring about the attraction and fusion of 

 gametes, are all bound up in the ultimate significance of sex. Som- 

 atic differentiations indicating male or female types are extremely 

 rare in Protozoa, but problems of gamete formation and fusion are 

 presented by Protozoa of all kinds and, so far as it applies to such 

 problems, the term sex and its connotations apply to the unicellular 

 animals. 



There is little reason to doubt that a fundamental effect of sex 

 is the perpetuation of the species through union of gametes; and 

 there is equally little reason to doubt that the same function under- 

 lies conjugation and fertilization generally in Protozoa. It is 

 tacitly understood by biologists that the sum total of conditions 

 leading to the production of eggs or of spermatozoa is typical of 

 the female or of the male, hence egg-like gametes in Protozoa are 

 regarded as the result of female activities, while spermatozoa-like 

 gametes come from males. This line of thought has led to the wide- 

 spread custom of describing macrogametes in Protozoa as female 

 and microgametes as male organisms. A difficulty has arisen, 

 however, in connection with the entire absence of visible differences 



