DESCRIPTION OF THE SEXUAL PRODUCTS. 23 



Very weak alkaline solutions stimulate the motions of seminal 

 filaments ; on the contrary, acids, even when they are very dilute, 

 produce death. Accordingly the motion becomes more lively in all 

 animal fluids of alkaline reaction, whereas in acid solutions it soon 

 dies out. 



HISTORY. The discovery that egg and seminal filament are simple cells is 

 of far-reaching import for the comprehension of the whole process of develop- 

 ment. In order to appreciate this to its full extent, it will be necessary to 

 make a digression into the historical field. Such a digression will acquaint us 

 with some fundamental transformations, which have affected our conception of 

 the essentials of developmental processes. 



In the last century, and even in the beginning of the present, ideas about the 

 nature of the sexual products were very indistinct. The most distinguished 

 anatomists and physiologists were of opinion that eggs agreed in their structure 

 in every particular with the grown-up organism, and therefore that they 

 possessed from the beginning the same organs in the same position and con- 

 nection as the latter, only in an extraordinarily diminutive condition. But in- 

 asmuch as it was not possible, with the microscopes of the time, actually to see 

 and demonstrate in the eggs at the beginning of their development the assumed 

 organs, recourse was had to the hypothesis that the separate parts, such as 

 nervous system, glands, bones, etc., must be present, not only in a very diminu- 

 tive, but also in a transparent condition. 



In order to make the process more intelligible, the origin of the blossoms of 

 plants from their buds was cited as an illustrative example. Just as already 

 in a small bud all the parts of the flower, such as stamens and coloured petals, 

 are enveloped by the green and still unopened sepals, just as the parts grow 

 in concealment and then suddenly expand into a blossom, so also in the de- 

 velopment of animals it was thought that the already present but small and 

 transparent parts grow, gradually expand, and become discernible. The doctrine 

 which has just been outlined was consequently called the Theory of unfolding, 

 or evolution. However, a more appropriate designation for it is the one intro- 

 duced during recent decennia -preformation theory. For the characteristic 

 feature of this doctrine is, that at no instant of development is there anything 

 new formed, but rather that every part is present from the beginning, or is 

 preformed, and consequently that the very essence of development the be- 

 coming is denied. "There is no such thing as becoming ! " is the way it is 

 expressed in the " Elements of Physiology " by HALLER. " No part in the animal 

 body was formed before another ; all were created at the same time." 



As the necessary consequence of a rigid adherence to the preformation theory, 

 it follows, and indeed was formulated by LEIBNITZ, HALLER, and others, that 

 in any germ the germs of all subsequent offspring must be established or 

 included, since the animal species are developed from one another in un- 

 interrupted sequence. In the extension of this box-within-box doctrine 

 (Einschachtelunyslehre) its expounders went so far as to compute how many 

 human germs at the least were concentrated in the ovary of mother Eve, and 

 thereby arrived at the number 200,000 millions. 



The evolution theory offered a point of attack for a scientific feud, inasmuch 

 as every individual among the higher organisms is developed by means of the 

 cooperation of two separate sexes. When, therefore, the seminal filament os 



