101 



fat in the sponge. Our data are (calculated per unit of time 

 and of sponge-volume) : 



1. The production of fat (p) is always proportional to the number 

 of colourless algae in the sponge (pag. 99). We know this number 

 of algae in the different stages of development of the tissue of 

 green Spongillae from light and colourless ones from darkness, 

 from Table 6, pag. 46 — 48 ; so we can immediately fix the course 

 of p: 2^ will increase in green and colourless sponges during 

 the development from very young to full-grown tissue, and 

 in colourless sponges it w411 always increase more than in green 

 ones ; at the end of, or shortly after, the gemmule-stage p will 

 decrease considerably and be about the same in green and 

 colourless sponges. 



The consumption of fat is determined by the motion of the 

 flagella in the chambers (ƒ) and by the development of the gem- 

 mules (g). From this follows: 



2. The consumption (ƒ) is proportional to the number of fla- 

 gellated chambers (we suppose now, that the average of their 

 flagellar-motions is always equal), the number of which is zero 

 in gemmules, but quickly increases in very young tissue, to 

 remain constant afterwards; /' does the same. Next — let us say 

 for simplicity's sake — f will be equal in green sponges in light 

 and in colourless ones in darkness. 



3. The consumption ((/) is only present and then high in the 

 very young tissue during the development of the gemmules, and 

 the same in green and colourless sponges. 



From these data follows : I. As p increases more during the 

 development of colourless sponge tissue than during that of green, 

 while (ƒ+(/) remains the same in both, there must be, l^t some- 

 what more fat in young (N.B. not very young!) tissue of colour- 

 less sponges than in that of green ones, 2'^^ in full-grown tissue 

 of colourless sponges much more fat than in that of green ones 

 (point 5, p. 87). II. l^t. As p increases during the development 

 of green and colourless sponge tissue while {f + g) remains 

 constant, the quantity of fat must increase in that period in both 

 sponges. 2"'i. As in both sponges p only considerably lowers at 



