38 GARY N. CALKINS. 



exceptional cases of continued activity may he mentioned here. 

 One, a giant form, was cut through the mouth at 11.15 A.M. 

 At 4 P.M. both fragments \\vre alive, the posterior fragment 

 swimming actively with the truncate end in advance, the anterior 

 fragment with the truncate end behind. On the following day 

 the smaller posterior fragment was dead, the other, anterior, 

 lived for ~2 hours when it was killed (no. 6). A second case, 

 cut in the same place, resulted in two fragments both of which 

 were alive after six hours. On the following day the smaller 

 one was dead but the other lived and gave rise to two types of 

 cells, one much smaller than the other and with a blunt posterior 

 end, while the other had the characteristic pointed end of Para- 

 meciuin caudal itm. In still another case the giant form was cut 

 posterior to the mouth, the posterior fragment being about 

 one half the size of the anterior part. Both parts were' alive 

 after six hours but both were dead on the following day. 



In all of these cases the organisms were treated for from fifteen 

 minutes to one half an hour with dilute neutral red, granules 

 in the cell being deeply stained at the time of cutting. What 

 effect the neutral red has upon the consistency of the protoplasm 

 I do not know, but certainly there was a marked difference in the 

 resistance to collapse after treating with this dye. In only two 

 other cases have I succeeded in keeping both fragments alive 

 after the operation on normal forms; in one case the smaller 

 fragment lived only ten minutes after the operation; in the other 

 case (Table II., no. 63) the original cell was treated with nuclein 

 before cutting, and both parts lived 24 hours. In the majority 

 of cases the smaller fragment collapses immediately after removal 

 of the knife. 



Several different races of Paramecium have been used, but 

 giant lonns on the whole have been selected because of the 

 greater ease of cutting. The smaller races and races of Parn- 

 ir< iinn aurelia do not allow sufficient play for the knife edge 

 and too great a /one is crushed by the operation. One race of 

 giant forms was obtained from brackish water at Roscoff, France, 

 for which 1 am indebted to Mile. Lip>ka. The other races have 

 been obtained from time to time from wild cultures in the 

 laboratory at Columbia I 'niver>it \ . As there 1 is little or no 



