THE GENESIS OF SEX. 169 



highest organisms each part or organ has but one function to perform, 

 and therefore does it thoroughly. You will observe that the final 

 cause, the end to be attained, the raison cFetre, in all this process is 

 better xcorl; a better result. Now, my object will be to bring the ori- 

 gin of sex under this general law — to show some of the steps, and that 

 each step was attended with better results. 



3. The Ki>"ds and Grades of Repeoduction. — You already 

 know that there are two fundamentally distinct kinds of reproduction, 

 viz., sexual and non-sexual — so distinct, indeed, that there seems to 

 be no possible connection between them. But remember that not only 

 are our distinctions in science far more trenchant than they are in na- 

 ture, but also that the distinctions in nature noio are far more trench- 

 ant than they were in early geological times. It is the peculiarity 

 of modern science, under the guidance of the doctrine of evolution, that 

 it loves to dwell upon the gradations rather than upon the distinctions 

 — it seeks for the missing links which make the chain of nature con- 

 tinuous. Now, there are several grades of sexual as well as of non- 

 sexual reproduction ; and through these grades they closely approxi- 

 mate each other. For example : sexual reproduction consists essen- 

 tially in the union of two different cells, the germ-cell and the sjyerm- 

 cell, to form one cell, the ovum. It is in the most literal sense a union 

 of diverse ticain to form one flesh. These two cells may be called the 

 sexual elements. This is all that is absolutely necessary to the idea of 

 sexual reproduction, even though the tico elements may be formed by the 

 same organ. But, further, the two elements are usually elaborated by 

 two distinct organs, viz., the ovary and the spermary. These are the 

 essential sexual organs. When these two organs are found in the 

 same individual, the condition is called bisexuality, or hermaphroditism. 

 Further, in the higher animals these two organs exist in different in- 

 dividuals. This condition is called unisexuality . Thus there are sev- 

 eral grades of sexuality. The sexual elements only may be separated, 

 or in addition the sexual organs may be separated, or in addition there 

 may be distinct sexual individuals. Any mode of reproduction not 

 answering to this description is non-sexual. But non-sexual reproduc- 

 tion also is of different grades. The lowest is fission. A cell or a 

 community of cells grows and divides itself into two. Each half, again, 

 grows and divides, and so on ad infinitum. Next above this is bud- 

 ding. A spot on the external surface of an organism groAvs more rap- 

 idly than contiguous spots, and forms a tubercle which grows into a 

 bud, assumes the form and structure of the parent, and finally sepa- 

 rates. In the next grade the budding is internal, from a sj^ecial organ 

 simulating an ovary, though not a true ovary, as in aphides. Finally, 

 in parthenogenesis we have a perfect ovary forming true ova and per- 

 fect embryo without fertilization or cooperation of the sperm-cell. 



Now, my object, more specifically stated, is to show — 1, that 

 the highest form, viz., unisexuality, was developed out of bisexuality 



