406 
Proceedings of Royal Society of Edinburgh. [sess. 
Species. 
5°-10° C. 
10°-15° C. 
15°-20° C. 
20°-25° C. 
Stylonichia myt. 
48 h. 
24 h. 
12 h. 
8 h. 
Euplotes pat. 
24 
J 5 
12 „ 
Onychodromus gr. 
48"„ 
24 ,, 
12 
6 „ 
Oxytricha fallax 
12 „ 
8 „ 
Colpidium colpoda 
12 „ 
8 „ 
Glaucoma scintillans . 
6 „ 
5 „ 
Balbiani * has also suggested that the volume of water in which 
the Infusoria are kept has a direct influence upon their power of 
increase. Thus he says that Paramecium aurelia requires to he 
kept in a cubic centimetre of water in order to realise its full 
power of multiplication. In view of the interesting results that 
E. Warren has obtained with different bulks of water in the case 
of Daphnia ( Q . J. M. S., 1900), it would seem as if similar treatment 
of the Infusoria offered a field in which good results could be 
obtained. 
It has long been known that the comparative regularity with 
which binary fission was carried out in favourable circumstances 
decreased as the period lengthened since the last conjugation. I 
have observed this phenomenon several times in the case of 
Paramecium caudatum and Stylonichia pust., but have been unable 
to express the gradually decreasing energy in the terms of any 
formula. On the other hand, it has been maintained that im- 
mediately after coming out of conjugation these two forms show 
a marked increase in the rate of fission — the expression of a 
surplusage of energy; of this phenomenon, however, I have 
never seen any trace. So far as I am aware, conjugation results 
in no difference in the after-rate of ordinary multiplication, and 
this also would appear to be true of light and darkness. 
Before proceeding to examine Maupas’ theory of binary fission 
and the recent attack upon it, I should like to refer to his 
specification of two distinct species of Paramecium aurelia and 
caudatum .f He gives a definite account of these two forms, in 
which the latter is described as possessing an elongated body, as 
* “ Observ. et exper. s. les phenom. de la reprod. fissipare chez les infus. 
ciliees,” Compt. rend. Ac. Sc. Paris , T. 50, p. 1191. 
t No reference is made for the present to other species, e.g., putrinum, 
, bursaria. 
