97 



So it seems, as if the sponge wonld dispose of two different 

 methods of digestion, l^i the often appearing sloiv digestion free in 

 the protojdasm of the amoehocytes, 2nd the less common quicJcer 

 digestion in food vacuoles of the sam,e cells. But is it not more 

 likely, tliat these two methods are only apparently diiïerent and 

 not really? With a slow digestion only littlc enzyme will be 

 secreted to the body which must be digested, so no vacuole- will 

 be formed around ; with a quick digestion on the contrary much 

 enzyme, consequently a vacuole is formed. The whole difference 

 between vacuole digestion and digestion free in the protoplasm 

 would thus only be founded on a difference in the rapidity, with 

 which the amoebocyte desires to digest a body (see also chapt. U). 

 With a normal regular course of the process of life there is no 

 need for a quick digestion, ouly little enzyme is secreted, conse- 

 quently no food vacuoles are formed. 



But if, for instance, a sponge is taken from its habitat to an- 

 other place, eg. an aquarium with water from the conduit, where 

 it will miss at any rate all kinds of nourishment — if not 

 the symbiotic algae, yet many other materials (dissolved in lake 

 water?) which probably are not less important — it is very 

 likely, that the sponge will theu try to supersede its lack of other 

 materials by a quicker digestion of the food, which is at its dis- 

 posal; in other words, the sponge will be going to secrete more 

 enzyme and form thus vacuoles round its food. Now, according 

 to point 19, exactly this thing happens with sponges in aquaria ! 

 Next the fact, that in newly caught Spongillae, according 

 to point 20, the food in young tissue is less quickly digested 

 than in full-grown ; it can be explained in several ways. But it 

 is not clear at once why, according to point 21, a quicker digestion 

 takes place in the tissues of colourless Spongillae in darkness (not 

 of Ephydatiae!) than in those of green ones in the light; for 

 there is probably no question at all about a stronger nutrition 

 of the green sponge . from the side of its green algae (p. 96), 

 while in the colourless sponge even some more algae are digested 

 in the protoplasm than in the green one (p. 96, 59, 46 — 48). So 

 one must come to the conclusion, that the colourless Spongilla 



