STRUCTURE AND LIFE-HISTORY OF COPROMONAS SUBTILIS. 105 
(1896) brought forward some interesting observations on 
Oxyrrhis (42). He discovered that the intra-nuclear 
division-centre—the nucleolo-centrosome—could be made to 
leave the nucleus and enter the cytoplasm by placing the 
animal in diluted sea-water. In the cytoplasm the division- 
centre might grow in size and even divide. These observa- 
tions are of great interest when considered in relation to the 
nuclear origin of the centrosome in Actinospherium and 
Acanthocystis, as demonstrated by Hertwig and Schaudinn. 
Mitosis was demonstrated in various Chlamydomonadina 
by Dangeard in 1898 (15). In the same year Calkins’ 
account (7) of the remarkable nuclear phenomena in 
Tetramitus appeared. In this animal the chromatic and 
achromatic parts of the nucleus are completely separate, 
except during division. ‘The former is in the form of chro- 
midia, the latter in the form of a large consolidated division- 
centre. Prowazek (85) and Dangeard (16) again worked 
out mitotic division in Polytoma in 1901. ‘The former 
described the presence of about eight chromosomes, the latter 
found not more than six. Prowazek also described the 
formation from the nucleus of a minute body—the “ento- 
some ”—which appears to act as a division-centre. Various 
euglenoids were investigated by Dangeard (17) in the following 
year, and one (Entosiphon) was described by Prowazek (87). 
It appears to have a method of division similar to Huglena, 
but more primitive. Dangeard (18) also described mitosis in 
Monas vulgaris. In 1904 Steuer gave us a description of 
mitosis in the euglenoid Eutreptia (48), and Awerinzew 
has just described anew (1) the nucleus and its division in 
Chilomonas. 
Amitosis is found in some forms. It was recorded in 
Monas guttula by Prowazek (1903 [86]), and by the same 
writer in Bodo lacerte in 1904 (89). From his description 
of the division—apparently amitotic—of the nucleus of 
Trichomastix it would seem that the axial rod plays the 
part of a directive centre. 
The various kinds of division, whose history I have just 
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