538 



brought the culture to an untimely end. It will be seen that 

 the usual rate of increase was one bipartition in 48 hours ; that 

 all the individuals of a given generation (especially during the 

 earlier bipartitions) divide at about the same time ; that the 

 rate of increase is accelerated from the 4th to the 9th biparti- 

 tion ; that, finally, discrepancies in the times of fission of the 

 offspring of each bipartition appear, and increase at each 

 subsequent fission. In passing from the 9th to the loth 

 bipartitions the interval between the fission of the two individ- 

 uals amounts to nearly four days. 



My culture experiments, though unsuccessful in producing a 

 long series of generations like the well-known experiments of 

 Maupas, at least demonstrate that it is possible to stimulate 

 Infusoria to a rate of increase beyond the normal, leading to 

 speedy deterioration of the race. It is probable that Stentors 

 are somewhat exceptional in this respect, and that such species 

 as Stylonichia piishilata and OnycJiodromtis grandis, in which 

 the time required for fission is much less than in Stentor, are 

 less susceptible to the pathologic effects of over-fecundity; but 

 these effects should, nevertheless, be taken into account. 



Since under rapid multiplication a Stentor culture deteri- 

 orates, under what conditions does the individual Stentor 

 attain its best development ? I gained a hint in the right 

 direction upon examining an old culture that had stood 



