1074 ^ 



D. The Defecation and Excretion. 



Very little is as yet known about these phenomena, particularly 

 because observalion and hypothesis are so much intermingled in the 



Fig. 5. The capture (2) and the carrying aside (3, 4) of a coarse 

 (food-) particle that remained sticking in the prosopyle (1,2), 

 by means of the layer of streaming plasma (pl.l.). The 

 individual cells of the choanocytes-layer (ch.l.) are not drawn ; 

 it contains numerous particles that have been taken up. 

 (Magnification about 100Ü times). 



literature. Mastekman ') found amoeboid cells loaded with feces 

 (carmine), which cells were on the point of being expelled at the 

 internal or external surface of the sponge, or had already been 

 expelled. Masterman says of these: "We have here an example of 

 a process of intracellular excretion for the removal of waste solids". 

 CoTTE ') describes defecation by the choanocytes and expulsion of 

 (and by means of) "cellules sphéruleuses". 



I have been able to establish in my living preparations that defe- 

 cation takes place on a large scale — and probably at the same time 

 also excretion of dissolved matter — by means of vacuoles situated 

 in cells of the canal-walls, whilst these cells themselves remain 

 behind in the wall of the canal (fig. 6a, b). The feces must 



1) Ann a. Mag. of Nat. History, Ser. 6 Vol. 13, 1894. 



2) Bull, scient. d. 1. France et d. 1. Belgique, T. 38, 1904. 



