410 Proceedings of Royal Society of Edinburgh. [sess. 
I have taken the figures for the first fortnight, hut greater 
regularity could have been shown if one had taken a fortnight at a 
later date. Fabre-Domergue confesses that he never succeeded in 
obtaining such regularity in any cultures that he undertook, and 
it seems to me that in so saying he intimates that he obtained 
a series of divisions that is much more natural than anything 
represented in Maupas’ mathematical tables. When cultures of 
Stylonichia or Paramecium are kept in glass vessels where they may 
have some small bulk of water in which to live, they do not 
multiply at this rate, or with such regularity. It is not my 
intention, however, to impeach Maupas’ tables as a whole, for 
with his results I find myself largely in agreement as against 
his latest adversary Joukowsky. Nevertheless, apart altogether 
from venturing to inquire how such exactness was acquired as is 
expressed in 935 Stylonichia, I would maintain that the results 
which Maupas first established are reached by a process of division 
that is far from regular, and depends to a great extent upon the 
individuality of the infusorian. Even under the happiest possible 
conditions (so far as one can judge), artificial or natural, binary 
fission does not proceed with that constant regularity that the French 
savant would ascribe to it. The following table, representing a few 
weeks of a short series, expresses, I believe, a more natural rate of 
progress than one would gather to be the case from Maupas’ table. 
The form experimented with was Paramecium caudatum , and in 
every case the series was commenced with two exconjugates. I 
have reckoned that case as one bipartition in 24 hours, where half or 
more of the creatures on the slide divided. 
[Table.; 
