93 PHILOSOPHICAL NOTES ON 



In Porphyra laciniata* Thuret observed that the vegetative 

 cells of the frond, by segmentation, became transformed into either 

 spores or antheridia. This was not all. For in abnormal .cases 

 the contents of the primitive cell changed partly into spores and 

 partly into antheridia, so that there does not appear to be any 

 fundamental difference, not only between vegetative and reproduc- 

 tive, but also between male and female elements. 



After the differentiation of vegetative and reproductive cells 

 had become established, inheritance produced by ages of fixed and 

 advantageous habits would normally prevent the ones from 

 exchanging functions with the others. But, as we observe in 

 abnormal cases, these functions may, under certain circumstances, 

 be exchanged. 



The sex functions appear to have been separated at a very 

 early period of living bodies, for Dallinger has shown thac 

 unicellular bodies, at certain periods, become what might be called 

 sperm and germ cells by fission. At all events, two simple cells 

 floating about in water, and indistinguishable from each other, 

 combine or fuse into a larger cell, which after a time bursts, and 

 liberates a number of germs. These develop into unicellular 

 bodies, which after multiplication by fission for a time, conjugate, 

 and repeat these phenomena. 



So even in these primitive bodies we have multiplication by 

 buds and multiplication by seeds or variable buds, just as we 

 have in the highest and most developed and complicated tree on 

 land. 



Separation of the sexes in distinct individuals must have 

 occurred also at a very early period, for we find it in seaweeds. 

 This separation might have very readily occurred accidentally, as 

 one might say. The atrophy of germ-cells in one individual and 

 the atrophy of sperm cells in another individual would have soon 

 established a dioecious race, if this separation were beneficial. 



The advantageousness of their separation would make this 

 feature permanent. Then inheritance, to a large extent, would 

 lock the door, and prevent the recombination of the sexes. In 

 other words, the complex conditions, under which organisms were 

 multiplying in their struggle for life prevented a return to con- 

 ditions suited to a simpler life, and in many cases the disadvantage 



* "Etudes phycologiques," pi. 31, p. 60. 



