312 BIOLOGY OF THE PROTOZOA 



jugation than before, a fact which Zweibaum (1921) interprets as 

 due to reorganization and the freeing of oxidases by nuclear disor- 

 ganization. To this mass of nucleo-proteins is also added three- 

 quarters (c. g., Paramecium) to fifteen-sixteenths (Uroleptws) of the 

 substance of the old micronuclei, which is likewise absorbed in the 

 cytoplasm. 



Not only is the old nuclear material broken down and distributed 

 but, in some instances at least, the formed metaplastids of the cell 

 are similarly destroyed and absorbed. This is well illustrated by 

 the disappearance of the old pharyngeal basket and some of the 

 cilia in Chilodon uncinatus (MacDougall, Fig. 112, p. 222). This 

 is perhaps relatively unimportant at conjugation since the same 

 thing happens at each division of the cell during vegetative life, 

 but it is evidence in support of the view that stabile substances of 

 the organism, substances that have accumulated with continued 

 vegetative life are reduced to labile substances at this significant 

 period of the life history. 



In a similar manner the many nuclei of Actinosphaerium eichhornii 

 (300 or more) according to Hertwig (1898) are fused or absorbed 

 prior to fertilization. As there must be a limit to the number 

 that fuse (if any?) the great majority of nuclei must be absorbed 

 in the protoplasm, for only a few (up to 20) become nuclei of gamonts 

 (see p. 307). 



In gregarines also there is a similar fragmentation of some of the 

 nuclei leading to collections of chromidia which appear to function 

 in the formation of sporoducts (see p. 239). In Mycetozoa and 

 Neosporidia also some of the nuclei are destroyed in connection 

 with the formation of accessory structures of the fruiting bodies 

 (elaters, sporoducts, spore capsules, etc.). 



The conclusion is forced upon us that this period of fertilization 

 is marked by far-reaching changes in organization. Some of these, 

 as in ciliates, have a prospective value for the young organisms 

 while others are differentiations serving a useful purpose for the 

 limited period of fertilization in organisms whose individual meta- 

 bolic activities are approaching the end, and these are evidence of 

 extreme specialization. 



(b) Metagamic Activities and Reorganization.— Under this heading 

 we include all changes which take place in the organism immediately 

 after formation of the amphinucleus. In ciliates the fragmentation 

 and absorption of the old macronucleus may continue for several 

 days after union of the gametic nuclei but the further activities 

 of the amphinucleus appear to be independent of the other happen- 

 ings in the cytoplasm. These activities have to do primarily with 

 the differentiation of the characteristic cell structures of the new 

 organism. Thus in Chilodon and other Chlamydodontidae a new 

 oral basket is formed and some if not all of the cilia are renewed; 



