302 THE PROTOZOA 



basis of a long series of experiments by Nussbaum ('84, '85), Gruber 

 ('86), Balbiani ('88), Hofer ('89), and Verworn ('88, '89, '91), which 

 have led to fruitful results. Amongst these, the most striking and 

 suggestive fact is, that without the nucleus, the process of digestion 

 cannot take place in any form of Protozoa. The beautiful and clear- 

 cut experiments of Hofer ('89) and Verworn ('91) have demonstrated 

 beyond a doubt that the digestive fluid is not prepared in the cyto- 

 plasm when the nucleus is absent. Hofer demonstrated that the 

 slimy secretion which Amoeba throws out to anchor itself before food- 

 taking is never formed by the enucleated portions, and Verworn ('88) 

 proved that enucleated pieces of Polystomella could not repair or regen- 

 erate the lost shell, while nucleated pieces quickly repaired it. Ver- 

 worn came to the conclusion, which seems to be demonstrated, that 

 enucleated protoplasmic masses cease entirely those chemical pro- 

 cesses by which products of the normal cell are used or formed. In- 

 deed, the generalization may now be made that no secretion takes 

 place in enucleated fragments. On the other hand, the nucleus by 

 itself, i.e. separated from the cytoplasm, has no longer the power to 

 regenerate the lost parts, and like the enucleated cytoplasm, soon dies. 

 "The nucleus needs the plasm, the plasm the nucleus," says But- 

 schli, "the activities of both are reciprocal, and one without the other 

 cannot live," 1 a generalization confirmed by Verworn's conclusive 

 experiments ('91). The processes of secretion, therefore, whether for 

 the purpose of digestion or for any other purpose in the life of the 

 unicellular organism, are expressed by the constant chemical inter- 

 change which goes on between the cytoplasm and the nucleus. 



Outside of secretion and reproduction, however, the usual functions 

 of motion, and those of the contractile vacuole, are performed nearly 

 as well by the enucleated as the nucleated fragments. Balbiani ('88) 

 observed that non-nucleated pieces of infusoria, while unable to regen- 

 erate the lost parts, were nevertheless capable of limited motion, and of 

 living and swimming about actively for several days, while the con tractile 

 vacuole continued its rhythmic pulsations. Hofer ('89) also observed 

 that non-nucleated pieces of Amoeba protons will form pseuclopodia 

 and live for some time after the operation in active motion, a point 

 which Verworn established in a striking manner in the case of Tha- 

 lassicolla nucleata. Here the central capsule, after extirpation of the 

 nuclei, forms a spherical mass which soon begins to assume the form 

 of a typical radiolarian. The vacuolated portion, however, only begins 

 to appear when degeneration sets in and the animal dies (Fig. 152). 

 That the enucleated portions require oxygen and can use oxygen is 

 shown by Verworn's negative experiments with enucleated Infusoria in 



1 ('88), p. 1642. 



