Origin of Sexuality 249 



constituents have yet been described, hereditary pecuKarities 

 of chromotophore color, wall formation and thickness, glycogen 

 formation, and other details, are all handed down by simple 

 division. 



Further, since these simple species have gradually varied, 

 so as to give rise to new species that not only differ in structure 

 but may inhabit different surroundings, it follows that chro- 

 matin was not primitively, and need not be, the only bearer 

 of heredity for protophytic types. So also chromatin for- 

 mation and heredity were not ultimate and sudden develop- 

 ments of certain primitive cells, but have evidently resulted 

 from slow modifications and condensations of energy, corre- 

 lated with the building up by that energy — on the principle 

 that we have called stereoenergics — of a greatly more complex 

 colloid, the chromatin, that has become the highly sensitive 

 or cognitic material of the cell. 



But we may now pass to another and more complicated 

 question that directly pertains to the present chapter. The 

 studies of many observers have revealed that certain cells of 

 several genera amongst Cyanophycece under definite seasonal 

 conditions, such as changes in moisture, temperature, and 

 light intensity, become more or less enlarged, their contents 

 become granular, the wreathed chromatin increases in quan- 

 tity, the wall becomes thick, often modified into several layers, 

 and not infrequently is pigmented. These "perennating cells," 

 then, correspond in every respect to the so-called ''akinetes" 

 of higher algse described later, except that they have no nucleus. 



Again, in Hyella and other genera, some of the normal cells 

 may increase in size, the contents become rounded off from 

 the parent wall, rupture of the latter occurs, and the entire 

 mass already enclosed in a new wall layer is set free. This 

 exactly corresponds to "aplanospore" formation, as described 

 below for the higher algae. 



Further, in the Champesiphonese and some Stigonemacese, 

 at certain seasons or under definite conditions a few or most 

 of the vegetative cells (p. 251) become enlarged, have their 

 protoplasm divided and redivided, till four to many rounded 

 masses have arisen inside each cell. These escape by rupture 

 of the parent-wall, each secretes a new membrane around 

 itself, and in time grows and divides to become a new indi- 

 vidual. So far as known none of the cells thus set free is pro- 



