166 Causes and Course of Organic Evolution 



in tlie plant laboratory by varying actions and reactions ^'itliout 

 and w-ithin the cells. It is highly significant, also, that they 

 are preponderatingly abundant amongst the flowering and 

 even more exactly the most evolved or sympetalous flowering 

 plants, where their number is as perplexing as is their con- 

 stitution varied. 



But few ^Nill deny that these are mainly accessory chemical 

 agents, which by their presence may intrinsically influence 

 cell life, or aid in its survival; they are in no sense a fixed hered- 

 itary characteristic of the entire plant world. 



If now, in view of the above conclusions, we try to approach 

 the question, wherein has evolution of the Caryota or of one 

 of them consisted .^^ an answer may best be got if we endeavor 

 to picture, as some writers have already done, the gradual 

 process of upbuilding of a complex multicellular plant or animal 

 from its egg. Such an egg can quite truly be called the uni- 

 cellular or temporary or starting evolving stage in the organ- 

 ism's existence, that corresponds to the entire life of such a 

 unicellular type as Chlamydomonas or Paramcecium. 



It may conduce better to future consideration if we limit 

 attention meanwliile to the vegetable world. The unicellular 

 plant Chlamydomonas may well be called a microcosm of those 

 great hereditary characters of the Caryota already spoken of. 

 It has abundant protoplasm surrounding a well defined nucleus 

 and nucleolus, specialized and highly energetic cilia during 

 the motile stage, chlorophyll that surrounds and aids the proto- 

 plasm in carbohydrate elaborating action except at the ciliary 

 end where the clear protoplasm alone is present, a sap vacuole 

 or two that permit diosmotic and possibly electrolytic changes 

 between the protoplasm and contained materials, a small mass 

 of red or reddish yellow pigment that during the motile stage 

 is aggregated into the "eye-spot." It has a cell wall that during 

 the resting state is a firm and easily recognizable cellulose 

 investment but is extremely delicate like the animal Avail 

 during the motile state. It elaborates sugar and starch in its 

 chlorophyll; it shows often globules or granules that give a 

 proteinaceous reaction. We may almost certainly conclude 



