118 LIFE AND DEATH. 



When in this case, the specific organization degenerates to 

 a certain extent, such changes depend in part upon the endeavour 

 to diminish as far as possible the size of the organism the pseu- 

 dopodia being drawn in, while the vacuoles contract and com- 

 pletely disappear. The degeneration may also, perhaps, depend in 

 part upon the secretion of the cyst itself, which implies a certain 

 loss of substance 1 . But degeneration chiefly depends upon the 

 fact that the encystment is accompanied by reproduction in the 

 way of fission, which seems to begin with a simplification of the 

 organization, that is, with a fusion of the numerous nuclei. It is 

 well known that many unicellular animals contain several nuclei 

 in other words, that the nuclear substance is scattered in small 

 parts throughout the whole cell. But when the animal prepares 

 for division, these pieces of nuclear substance fuse into a single 

 nucleus which itself undergoes division into two equal parts 2 during 

 the division of the animal. It is evident that the equal division 

 of the whole nuclear substance only becomes possible in this way. 



There are, however, numerous cases which prove that the bodies 

 of encysted animals may retain, during the whole process, exactly 

 the same structure and differentiation, which were previously 

 characteristic of them. Thus the large Infusorian Tillina magna, de- 

 scribed by Gruber, can be seen through the thin-walled cyst to 

 retain the characteristic structure of its ectoplasm, and the whole of 

 its organization. Even the movements of the enclosed animal 

 do not cease ; it continues to rotate actively in the narrow cyst, 

 as do the two or four parts into which it subsequently divides. 

 Such observations prove that Gotte's view that ' every characteris- 

 tic of the previous organization is lost/ is quite out of the question 3 

 (1. c., p. 62). 



1 This is of importance in so far as single individuals might be thus compelled to 

 encyst even when the existing external conditions of life do not require it. The 

 substance which Actinosphaerium, for example, employs in the secretion of its thick 

 siliceous cyst must have been gradually accumulated by means of a process peculiar to 

 the species. We can scarcely be in error if we assume that the silica accumulated 

 in the organism cannot increase to an unlimited extent without injury to the other 

 vital processes and that the secretion of the cyst must take place as soon as the 

 accumulation has exceeded a certain limit. Thus we can understand that encyst- 

 ment may occur without any external necessity. Similarly, certain Entomostraca 

 (e.g. Moina) produce winter-eggs in a particular generation, and these are formed 

 even when the animals are kept in a room protected from cold and desiccation. 



2 Upon this point Professor Gruber intends to publish an elaborate memoir. 



3 This view has not even been proved for Actinosphaerium, upon which Gotte 



