102 



the end of, or shortly after, the gemmule-stage, but (/" + g) di- 

 minishes already immediately in that stage to about zero the 

 quantity of fat must be very high (maximal) in that period. 

 S'd As in both sponges j^ is a minimum in very young tissue, 

 while here (f + g) reach their maximum, the quantity of fat must 

 lower considerably (be minimal) in that period (point 6, p. 89). 



From this we see: 1st How perfectly the experimentally stated 

 facts about the quantity of oildroplets, present in the sponge tis- 

 sues, correspond with the theoretical calculations of the quantity of 

 fat, which we could make from the co-operation of the factors 

 that proved to rule the production atid the consumption of fat in 

 the sponge. From this follows again: 2Q'i That the quantity of oil- 

 droplets in the sponge tissue must be in fact proportional to the 

 total quantity of fat that is present (see p. 100). 



Undoubtedly, such calculations could be made also for the 

 carbohydrates in the sponge tissue. I do not dispose, however, of 

 sufficient facts to test their result. We might still conclude that 

 the fact mentioned under point 13 (p. 92), that the globules 

 which can be stained brown by I in the amoebocytes of colour- 

 less sponges are perhaps somewhat more numerous than in those 

 of green ones, will have to be explained in the same way as we 

 did here for the oildroplets. 



At last the question: What is the reason of the dying of the 

 green symbiotic algae within the amoebocytes? Probably one will 

 be inclined to see this in the fact, that the amoebocytes digest 

 the algae, as we saw above. Certainly, the amoebocytes are sure 

 to digest the dead algae, but have they also purposely killed all 

 of them — i. e. to make them serve as nutrition ? Or does the 

 sponge digest them, because (after) all (or some) algae were al- 

 ready dead for quite a different reason ? Perhaps one considers 

 this at first sight as a singular and rather far fetched supposition. 

 After due consideration, however, one will acknowledge, that this 

 supposition is not at all so singular and far fetched; on the con- 

 trary, that one certainly must consider this possibility too. For 

 the rest I will immediately admit, that the whole question about 



