534 BIOLOGY OF THE PROTOZOA 



the same odd number by Leger and Diiboscq (1909) in Nina 

 gracilis; while 3 were found by Shelhiek in Monocystis omta (1912). 

 Such odd ninnbers are not difficult to interpret if reduction takes 

 place at the first metagamic dixision but they lead to questionable 

 hypotheses of "odd chromosomes" (Leger) "accessory chro- 

 mosomes," etc., if reduction is interpreted as taking place prior to 

 fertilization. Trouboukoff's (1914) account of reduction in the 

 macrogamete as occurring either before, during or after fertilization 

 in Stenophora jiili is unintelligible under either interpretation. 



Apart from Sporozoa the only evidence of zygotic meiosis in 

 Protozoa is given by Pascher's (1916) account of Mendelian segre- 

 gation in Chlamydomonas. This evidence is not cytological but 

 is furnished by the make-up of the Fo generation (see p. 577). 



3. Metagamic Phenomena. — While the meiotic processes are 

 probably universal accompaniments of fertilization they do not 

 comprise all of the phenomena taking place at this period. Evi- 

 dences of disorganization are apparent in the cell quite independent 

 of the gametic nuclei. Metagamic activities involving reorganiza- 

 tion of the protoplasm are equally characteristic of the fertilized 

 cell and lead to the production of young organisms with full potential 

 of vitality. Disorganization and reorganization, although probably 

 closely related, are different in character and will be discussed 

 separately. 



B. Disorganization and Reorganization. — (a) Phenomena of Dis- 

 organization.^ The destruction of the old macronucleus in Infusoria 

 is one of the most significant of the phenomena attending conjuga- 

 tion (Fig. 200, p. 496). Here is an organ of the cell which is generally 

 regarded as intimately connected with metabolic activities of the 

 organism; which has functioned throughout vegetative life of the 

 race and has divided with each di\'ision of the cell. Yet at con- 

 jugation the macronucleus degenerates through hypertrophy and 

 fragmentation and the fragments are ultimately absorbed in the 

 protoplasm. The process is fundamentally the same in all ciliates 

 dift'ering only in details. 



If the organization of a ciliate is dependent upon the specificity 

 of the proteins, carbohydrates, fats, salts and water which enter into 

 its make-up then this large bulk of nucleo-proteins distributed to 

 all parts of the cytoplasm, must bring about a markedly different 

 matrix with which the new amphinucleus and its products are to 

 react. Zweibaum (1922) concluded that products of metabolism 

 during vegetative activity gradually poison the nuclear substances 

 so that both synthetic and oxidizing activities are weakened, but 

 at conjugation and with fragmentation of the macronucleus the 

 contained ferments are freed from their toxic bonds, and activity 

 is fully restored. The intake of ox\gen is much greater after con- 

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



