492 



THE AMERICAN NATURALIST [Vol. LVI 



other directions, may we not be well satisfied if, for the 

 time, we can say that the formation of carbohydrates and 

 proteids has been brought within the categoW of ordi- 

 nary chemical operations, which can occur without the 

 previous existence of living substance? 



To return once more, however, to the free-swimming, 

 autotrophic flagellate. In the early stages of its history 

 the loss caused by sinking, and so getting below the in- 

 fluence of light and the possibility of further growth, must 

 have been enormous. "We may conceive a constant rain 

 of dead and dying organisms falling into the darker re- 

 gions of the sea, and thus a new field would be offered 

 for the development of any slight advantages which par- 

 ticular individuals might possess. Under such conditions 

 we may suppose that the holozoic or animal mode of nu- 

 trition first began in the absorption of one individual by 

 another one, with which it had chanced to come into con- 

 tact. If the one individual were more vigorous and the 

 other moribund, we should designate the process feed- 

 ing," and the additional energy obtained from the food 

 might well cause the individual to survive. If the two 

 individuals which coalesced were both sinking from loss 

 of vigor, the combined energy of the two might make pos- 

 sible a return to the upper water layers, where under the 

 influence of light growth and multiplication would pro- 

 ceed, and we should, I suppose, designate the coalescence 

 conjugation," or sexual fusion. 



Other individuals, again, sinking in shallow water, 

 would stick to solid objects on the sea-floor, whilst the 

 flagellum continued to vibrate. The current produced by 

 the flagellum under these conditions would draw towards 

 the organism dead and disintegrating remains of its fel- 

 lows, and again we should have ingestion and animal 

 nutrition. At this stage we witness the definite passage 

 from plant to animal life. A further stage is seen when 

 a cup-like depression to receive the incoming particles of 

 food is formed at the base of the flagellum, to be followed 

 still later by a definite mouth. 



Any roughening of the external surface of the swim- 



