caS JOHNSON. [Vol. VIII. 



the temperature was not noted. Another, at temperature of 

 22° C. gave the following remarkable record : 



The irregularities in pulsation are quite as marked in 5. 

 cceruleus as in 5. roeselii. At 19° C. I have noted an interval 

 of 2 min. 20 sec. for four consecutive contractions. Another 

 specimen yielded the following record (temp. 21° C): 3 min. 

 30 sec, 3 min. 27 sec, 3 min. 35 sec, 3 min. 30 sec, 3 min. 

 25 sec, 3 min. 30 sec. We here detect what has been 

 apparent in some of the foregoing records — a tendency to 

 alternation of long and short diastoles, and constant recurrence 

 of periods of same duration. It will be also noted that the 

 rate of pulsation is much slower in 5. cceruleiis than in 5. roeselii, 

 whatever the temperature. 



It is apparent that the differences in the rate of pulsation, 

 however dependent upon temperature, are also matter of 

 individual variation, just as we have seen to be the case with 

 fission and regeneration. Hence observations undertaken to 

 ascertain the variation in pulsation of the contractile vacuole 

 coincident with changes in temperature must be made upon 

 one and the same individual, and, furthermore, one in which 

 the pulsations have been found to be isochronous. 



F. Merotomy} 



The Stentors have been the subject of extensive merotomical 

 experiments, having been used for this purpose by Gruber ('86), 

 Balbiani ('88), Verworn ('89), and again very recently by 

 Balbiani ('92). My own experiments in merotomy were made 

 upon the Blue Stentor, which is, indeed, the most favorable 



1 The term merotomy (" merotomie ") was coined by Balbiani ('88) to designate 

 the operation of artificial division upon unicellular organisms, with the purpose 

 of observing the subsequent fate of the artificially-produced individuals, or 

 " merozoites." In place of this almost unpronounceable word, I propose the 

 term merozoon, formed on the analogy of Protozoon, etc. 



