THEORY OF SEX- ITS NATURE AND ORIGIN. 



121 



colony of cells produces either female or male elements, thus representing the 

 beginning of an entirely unisexual many-celled organism. 



While the above cases also involve the problem of the origin of 

 fertilization, which is left over for the present, they confirm most clearly 

 our general conclusion that preponderant katabolism or anabolism are 

 the ruling characteristics of male or female respectively. 



V. Nature of sex as seen in Origin among Animals. — 

 Among the Protozoa, also, we can trace the beginnings of the same 

 "dimorphism" between male and female. A union between similar 

 cells is of course frequent, but that is not at present to the point. 

 What we refer to, are the numerous cases, especially among flagellate 

 and vorticella-like infusorians, where the two individuals which unite 

 are quite unlike one another both in form and history. "There can 

 be no doubt," Hatchett Jackson remarks, "that the process is 

 essentially a sexual one ; when the individuals are invariably different, 

 there is no reason why the terms male and female should not be 

 applied to them." In some cases we find as before that a small active 

 katabolic unit combines with a larger, more passive, and anabolic 

 individual. 



Fig. 37. — Vorticella, the Bell-animalcule. — a, the normal 

 individual; 6, its division into two; c, the division 

 accomplished: d, the further division of one of the 

 halves into eight small (male) units; <•, a minute 

 individual uniting with one of normal size. 



In the bell-animalcule, which grows so commonly on the water- 

 plants of our ponds, a minute free-swimming unit, formed as one of 

 the results of repeated division, unites with a stalked individual of the 

 normal size. In the related Epistylis, Engelmann has described how 

 an individual divides first of all into two cells. One of these remains 

 as such (like an ovum), the other repeatedly divides (like a mother- 

 sperm-cell) into numerous minute units. One of these subsequently 

 unites with the undivided cell, and Engelmann does not hesitate to call 

 the different elements male and female. In some radiolarians (for 

 example, Collozoum), dimorphic spores — large and small — have been 



