126 Asa Arthur Scheie ffer 



In the first experiments, organisms which are readily eaten by 

 Stentor were altered as far as their chemical nature was concerned. 

 Some were cooked, some soaked for a considerable time in alcohol, 

 others in iodine, osmic acid, mercuric chloride, tannic acid, etc. 

 Euglenae, Tjachelomonas, and very small paramecia were the 

 organisms employed for these purposes. After they had been 

 treated with the chemicals mentioned, they w^ere thoroughly 

 washed and sucked up into pipettes. Hungry Stentors were iso- 

 lated; then normal living organisms, and also those treated with 

 the chemicals, were fed to the Stentors in mixed order, as was done 

 in the first series of experiments. In no case were the chem- 

 ically treated organisms rejected while the living were eaten. 

 Some Stentors ingested all the organisms, and others rejected some 

 of the living and some of the chemically treated, while the rest, 

 including organisms of both kinds, were rejected. 



It was found in previous experiments that Stentor could dis- 

 criminate between Phacus triqueter and P. longicaudus, and 

 between Trachelomonas hispida and T. volvocina, etc. In the 

 experiment just preceding Stentor did not discriminate between 

 living organisms and organisms killed with osmic acid, iodine, 

 etc. Now it seems improbable that Stentor selects upon a chemi- 

 cal basis, since it is hard to understand how there could be a 

 greater difference in "taste" between living Phacus triqueter and 

 living P. longicaudus, where there was selection, than between 

 living Phacus triqueter and specimens of P. triqueter killed with 

 acids, iodine, etc., where there was no selection. 



But to test this result further another set of experiments was 

 performed in which the form and surface texture of food organisms 

 was changed to a greater or less extent, but the chemical nature 

 was left, as nearly as possible, in the same state as in the normal 

 organism. Paramecia and Euglen^e were used for these purposes. 

 By means of very small platinum knives these organisms were cut 

 into halves or quarters, or even smaller pieces, and then fed in a 

 stream with whole living organisms of the same species. There 

 was no discrimination. The pieces were eaten as readily as the 

 whole specimens. Many of these organisms were then mashed 

 and minced into very fine fragments so that the original form and 



