536 



JOHNSON. 



[Vol. VIII. 



not, as Maupas supposes, a normal rate, was shown by the fact 

 that it could never be maintained for any length of time. 



I soon became convinced that the slide-culture method, 

 however successful it might be with other species of Infusoria, 

 was not adapted to Stentor. So I made cultures in large 

 watch-glasses, each covered with another watch-glass to prevent 

 evaporation. Most of the watch-glass cultures were supplied, 

 in addition to the food-infusoria, with unicellular green algae, 

 usually a species of Scenedesmus. The rapid growth of these 

 algae kept the water pure, and to some extent furnished food 

 for the Stentors. But the watch-glass cultures were only in a 

 slight degree more successful than the slide-cultures ; for 

 while I was able to raise Stentors on the slide to the 7th or 

 8th generation, I did not succeed in getting any colony in a 

 watch-glass beyond the loth. 



One of the most rapid multiplications that I have noted was 

 of a culture started in a 2-inch watch-glass with a single 

 Blue Stentor, Dec. i, 1891. Following is the record of the 

 culture: — 



Individuals. 



(One was isolated.) 

 2 



4 



8 

 16 

 32 



58 



Temp 



I5°-22= 



BiPARTlTIONS. 

 I 



2 



3 



4 



5 

 6 



7 



It is seen that there were two intervals when bipartitions 

 were 48 hours apart, whereas the rest were at the minimum 

 interval of 24 hours. After attaining the 7th generation the 

 Stentors almost ceased to multiply and many died. The 

 culture having received abundant feed from beginning to end, 

 lack of nutriment could not be considered as the cause of its 

 decadence. 



What was the effect of such frequent bipartitions upon the 

 individual ? Neither in this nor in any other instance of 



