1900 - 1 .] Dr J. Y. Simpson on Binary Fission of Ciliata. 417 
lateral expansion of the anterior half. This and an earlier stage 
are shown in fig. 4. In this peculiar condition it remained with 
slight modifications about another week, but was dead by the 28th. 
Up till quite recently Maupas’ classical work has been permitted 
to go comparatively unchallenged. In the Verhandlungen des 
Naturhistorisch-Medizinisclier Vereins zu Heidelberg , however, D. 
Joukowsky publishes certain “ Beitrage zur Erage nach den 
Bedingungen der Vermehrung und des Eintritts der Konjugation 
bei den Ciliaten,” which go contrary somewhat to the received 
views. 
Joukowsky’s observations were made upon Pleurotricha lan- 
ceolata — a form allied to Stylonichia — Paramecium caudatum , and 
Paramecium putrinum. He says that he got irregular divisions 
at first : only after a month did the forms divide regularly. After 
the numbers on a slide had reached one hundred, division was 
slower. I have already referred to this question of regular and 
irregular division. My own experiments were more than once 
carried on considerably over two months, and I did not find any 
greater regularity after the first four weeks than I did during that 
time. Nor is it easy to see why this should be so. To imagine 
that these infusorians will settle down after a month into 
regular methods of division simply* means failure to appreciate the 
conditions of the experiment. Joukowsky indeed says that the 
abnormalities in the division rate were due to the abnormal 
relations in which the creatures live. Bacteria generate and 
hinder ordinary division, and one may well suppose that the 
secretions and excretions of the creatures themselves may be 
ultimately dangerous in such a circumscribed area. But then this 
investigator deliberately states that after a month the divisions 
became regular; and yet we are not led to believe that he had 
found any means of overcoming the difficulties in which he sees the 
cause of the earlier irregular divisions. Obviously, therefore, they 
cannot have played the part that he imagines. I may also 
mention here that Maupas, while making these largely statistical 
experiments in binary fission, employed cover-glasses on his slides 
in the damp chamber. This appears to me to have been the 
introduction of an altogether unnecessary artificial condition. So 
far as regards the observation of the mere rate and other simple 
