Origin of Sexuality • 247 



osmotic membrane, where it comes into contact with the solu- 

 tion. This spherical membrane is extended by osmotic pres- 

 sure, and grows gradually larger. Since the area of the surface 

 of a sphere increases as the square of its radius, when the cell 

 has gro^\ai to tmce its original diameter, each square centimeter 

 of the membrane T\'ill receive by diffusion but a quarter as 

 much of the membranogenous substance. Hence, after a 

 time, the membrane will not be sufficiently nourished by the 

 membranogenous substance, it wdll break down, and an aper- 

 ture will occur through which the interior liquid oozes out, 

 forming in turn a new membranous covering for itself. This is 

 the explanation of the fact that all liAdng organisms are formed 

 by colonies of microscopical elements, although we must not 

 forget that Nature often produces similar results in different 

 ways." 



In the primitive plant cell, as in nearly all higher ones, a 

 phase in such osmotic tensions has been reached where the 

 living substance of the cell secretes an interior new strength- 

 ening pellicle, between halves of the distended mass, before 

 rupture of the proceeding one occurs, as the researches of 

 Schimper and Strasburger have demonstrated. All known 

 facts then seem to indicate that division was, of necessity, 

 the simplest and most primitive mode of multiplication. As 

 Leduc's account also would suggest, budding, as seen in the 

 yeast and other plants, is a variety of the same process funda- 

 mentally. 



When repeated divisions in one plane succeed each other, 

 and the resulting cells remain in contact, a filament is formed, 

 and then, as often happens \\dth the higher or thread types 

 of the Cyanophycese, multiplication may be due to breaking 

 across of a part of the thread at some point where weight of part 

 of the thread causes bending and compression of a cell with 

 resulting rupture. So, in simple unicellular Cyanophyceae and 

 even in thread forms, division in some way is the only method 

 of multiplication known. 



But, when we reach the Nostocacese, Chamaesiphonacese, 

 and Stigonemacese of the Blue-green Algae, a most interesting 



