152 Causes and Course of Organic Evolution 



to great fineness and agility of action. The sperm cells of 

 all the "cryptogams" and of some gymnosperms possess them, 

 but clearly they have been absorbed in the sperm nucleus of 

 the highest flowering plants. Their formation on various 

 motile spore-cells of algae is frequent also. Amongst animals 

 the more active life of the cell individual, as in Infusoria and 

 Rotifera, is accompanied by ciliary growth, but in the Metazoa 

 cilia appear and disappear again according to environal rela- 

 tions. Thus all acknowledge that the varying degree of cili- 

 ation of invertebrate larval forms represents transition phases 

 from a common ancestral holotrichous state. 



As to the minute structure and innervation of cilia, it seems 

 probable that these arose primitively, as in the Schizophycese 

 noted above, from simple protoplasmic extensions. But their 

 origin from a blepharoplast at least in some cases, and the 

 chromatin nature of that body, as the writer would consider 

 it, are in keeping with the view that possibly all cilia of the 

 Caryota are connected with and innervated from cognitic 

 energy in chromatin substance. 



The nucleus and nucleolus mil receive detailed consideration 

 later (chap. 10), but here it may be said that in structure, com- 

 position, staining capacity, changes undergone during division, 

 and to a large measure also during fertilization activity, the 

 phenomena are fundamentally alike for the Caryota, though 

 varying minor specific modifications are at times shown. In 

 all of the great groups sexual phenomena, alike in the narrowest 

 and the widest sense, appear with, and remain associated with, 

 the fundamental constituent of the nucleus and nucleolus 

 kno^^Tl as the chromatin, wliich remains the same throughout 

 the plant and animal kingdoms; but which develops specific 

 peculiarities in forming varying numbers of chromatin seg- 

 ments during cell-division, in the pathways these pursue during 

 division, and in their connection with the nucleolar mass. 



Pure chlorophyll of green plants agrees throughout in struc- 

 ture, spectroscopic characters, behavior to agents, functional 

 activity, and decomposition changes. Equally true is it that, 

 at different evolving stages in the plant world, groups of plants 

 — flowerless and flowering — tend to become saprophytic or 

 parasitic, owing to gradual accustomment to absorption of 

 organic food from other living or dead plants or animals. In 

 the process the chlorophyll gradually ceases to form and ulti- 

 mately pale yellow or perfectly white plants result. The 

 successive stages in this process shoTVTi by about a dozen fam- 

 ilies of flowering plants are instructive from the common stand- 

 point of devolution. 



