94 



BIOLOGICAL LECTURES. 



latter is furnished to the cilia by the disintegrating excreto- 

 phores; the food is constantly carried to the surface of the 

 cell in the form of small, pale granules, which I have mentioned. 

 You perceive how beautifully all the wheels in this process fit 

 together. The cell is active; waste products are formed; these 

 enter into new chemical combinations with the substances in 

 the excretophores. Oxygen is freed by this, and the cell thus 

 obtains, even through the agency of its own waste products, 

 fresh oxygen which stimulates it to continued activity. At the 

 same time the noxious waste products are taken care of and 

 washed into the funnel cavity. The peculiar arrangement of 

 the cytoplasmic threads in the cell is possibly due to the con- 

 stant mechanical action of the food stream which flows toward 

 the ciliated surface. 



I have endeavored to represent these different correlated 

 processes by a diagram, which is indeed extremely schematic 

 and very defective in detail, but which shows my idea of the 

 processes better than any verbal description (Fig. 6). 



R represents the receptaculum, the rectangle A the funnel 

 cell body, B the ciliary apparatus on the surface of the latter, 

 and E the approaching excretophore before disintegration. 



In ^ I have given the factors for metabolic activity: 6> = 

 Oxygen, P = Protoplasma, and F=^ Food. 



Plasma plus oxygen enters upon the process of destructive 

 metabolism, the terminal product of which is a substance 

 (P-W) capable of regeneration, or, better, endowed with 

 reconstructive affinities, and a waste product JV. The food F 

 may by the action of the nuclear substance be divided into, 

 say, two parts F' and F". 



F' enters with P-JV upon the process of constructive 

 metabolism (probably under the influence of the nucleus), the 

 final result of which is the original Plasma P. The fate of the 

 waste product IV is to be considered later on. 



In B we have the given factors: C^ ciliary substance, and 

 O = oxygen. These two substances affect each other also in 

 the sense of destructive metabolism, the result of which is M, 

 ciliary motion ; IV", waste product ; and C- W", a reconstruc- 

 tible substance similar to P-W in A. F" , the second part of 



