88 BIOLOGICAL LECTURES. 



and the isolating drops around the excretory granules, the latter 

 by a soaping process. There are numerous possibilities as to 

 the chemical character of these disintegration products, and it 

 would be a vain attempt for me to go into any further discus- 

 sion of this matter. 



One thing is evident, namely: the excretory granules repre- 

 sent final unalterable products and remain in a solid state after 

 all the other substances in the cell have been dissolved. 



The nucleated part of the excretophores which was left 

 behind undergoes a similar fate, but my observations on this 

 point are not so conclusive as those concerning the fate of the 

 pseudopodia. This is mainly due to the fact that in certain 

 stages it is hard to distinguish between parts of the cell possess- 

 ing a nucleus and those without one. The nucleated cell body 

 continually sends forth pseudopodia, which become detached, 

 and finally very little cytoplasm is left around the nucleus. It 

 seems that the presence of a certain volume of cytoplasm is as 

 necessary for the life of the nucleus as the presence of the 

 latter is for the cytoplasm, because during this gradual loss of 

 surrounding cytoplasm the nucleus gradually loses its normal 

 structure, the chromatin granules cluster together, the mem- 

 brane disappears and the nuclear network becomes dissolved. 

 Finally, we observe in sections only a dark, homogeneous mass 

 representing the nucleus which it is nearly impossible to detect 

 in the living cell. The remains of the cytoplasm disintegrate 

 in the same way as the pseudopodia, and it is probable that the 

 nucleus also finally breaks up into granules and is carried away 

 in the form of debris by other excretophores. 



I have not come to any definite conclusions as to the fate of 

 the dissolved cytoplasm and the colorless drops; it is probable 

 that they consist of nutritive material in fluid form and are 

 absorbed by the surrounding tissues. 



Finally, I should like to mention that this whole conception 

 of the origin of the pigment is not only based upon the micro- 

 scopical study of stained sections and of teased preparations of 

 the living animal, but has also been fully confirmed by experi- 

 ment. I added to the food of the animals a quantity of fine 

 carmine powder, an absolutely indigestible substance, and tried 



