3i8 RESEARCH IN PROTOZOOLOGY 



Concerning the behavior of these two nuclei of the sporoplasm 

 there have been a number of observations which may be put under 

 the following groups : 



a) The tzifo nuclei fuse into one. Several investigators noticed 

 one or two nuclei in the sporoplasm of the spores found in a single 

 cyst of a myxosporidian (Schroder, 1907, Keysselitz, 1908, Mer- 

 cier, 1909, Auerbach, 1910, Erdmann, 191 7, Georgevitch, 191 5, 

 Kudo, 1922, 1926, etc.). The spore containing the sporoplasm with 

 a large nucleus is considered by these investigators as more mature 

 than that with binucleated sporoplasm, that is to say, the two nuclei 

 of the sporoplasm are considered to have fused with each other. 



b) The binucleafe sporoplasm dizndes into t'wo uninucleate amoe- 

 bulce and there is no fusion of the nuclei. Schuurmans-Stekhoven 

 (1919) who studied Myxobolus szvellengrebeli proposed this view, 

 which if it really occurs in this species appears to be a unique 

 process, since no other observer has agreed with the view. The 

 same investigator (1920) does not seem to uphold this view in his 

 study of Myxobolus destruens. 



10. Problems concerning the nuclei of the trophozoite. All in- 

 vestigators agree that the youngest trophozoite is a uninucleate 

 form. The nucleus undergoes multiplication. In the well-studied 

 forms, there are two types of nucleus, vegetative and generative. 

 Mavor (1916), Davis (1916) and Kudo (1922), all working on 

 coelozoic forms, noted that the first division of the trophozoite 

 nucleus results in production of a generative and a vegetative 

 nucleus. In the polysporous histozoic myxosporidia, the two types 

 of the nucleus have also been noted, but their early history starting 

 with the nucleus in the uninucleate trophozoite awaits future 

 investigations. 



As to the transformation of the vegetative nucleus to the gener- 

 ative, there are two views. Davis (1916, 1923) and Bremer (1922) 

 hold that the vegetative nucleus does not give rise to the generative 

 nucleus, after it has differentiated as such, while Schroder (1907), 

 Lo Giudice (1912), Georgevitch (1917), Kudo (1922, 1926) and 

 others maintain that the vegetative nucleus gives rise to the genera- 

 tive nucleus by further divisions. According to Debaisieux ( 1924, 

 1925), two vegetative nuclei fuse to form a generative nucleus. All 

 agree, however, that the vegetative nucleus divides. The division 

 appears to be amitotic according to Kudo (1922, 1926), Davis 

 (1923) and Debaisieux (1924, 1925). 



