STRUCTURE AND LIFE-HISTORY OF COPROMONAS SUBTILIS. 93 
majority of Flagellata, we can still say with Senn (47): 
“Uber die Art der Vacuolenvermehrung wissen wir nichts 
naheres.”’ 
Transverse or multiple division has never been observed. 
A large number of cases of the former which have been 
described among flagellates are almost undoubtedly to be 
regarded as late stages in longitudinal division. There can 
be no doubt that it does occur in some forms, however, e. g&. 
in Oxyrrhis. And amongst the Chlamydomonadina, accord- 
ing to Dangeard (14), division may be either longitudinal or 
transverse, the result being dependent upon the position of 
the achromatic spindle during mitosis. ‘The plane of division 
is at right angles to this; and the position of the spindle 
itself is determined by the relative positions of the cell- 
protoplasm and the chloroleucite. 
After longitudinal division has continued for a period 
varying from about two to six days, a considerable number 
of the monads will be found to be conjugating. I will there- 
fore now describe this process and its sequele. 
(2) Conjugation and Encystment. 
The conjugating individuals are indistinguishable from 
their forerunners. Every monad, apparently, is a potential 
gamete. No difference, therefore, exists between the gametes 
themselves—that is to say, they are isogamic, displaying no 
sexual differentiation. It is true that occasionally one of the 
conjugants appears to be distinctly smaller than the other. 
But then it must be remembered that in cultures of the 
monads a great variation in size is often observable, and it is 
most probable that size-variation in this case is merely an 
expression of individual differences in rate of growth and 
food assimilation. | 7 
Conjugation may be easily watched in a hanging-drop 
preparation, though it is difficult to make out anything of the 
nuclear phenomena by this means, owing to the activity of 
the monads. The process, as seen in the living animals, may 
