Amicronucleate Infusoria. 



29 



without morphological micronuclei. Ten of the lines were all 

 isolated from a "wild" mass culture of the same species, Urostyla 

 grandis, found in a laboratory aquarium. Six of these lines were 

 amicronucleate. All of the lines of all of the species have bred 

 true with respect to the character in question and one amicro- 

 nucleate line at present is at the I02d generation. 



Similarly a culture of Paramecium caudatum, which the present 

 writer supplied a year ago to a course in protozoology for the 

 study of the nucleus, failed to reveal a micronucleus, although in 

 other races the micronucleus was readily demonstrated. 



The apparent conclusion is that a distinct morphological micro- 

 nucleus is a variable character among different races of the 

 common free-living Ciliates and this, obviously, leads to many 

 interesting problems in relation to conjugation and endomixis. 1 



18 (1600) 



A preliminary report on the experimental production of sarcoma 

 of the liver of rats. 



By F. D. Bullock, M. R. Curtis, and G. L. Rohdenburg. 



[From Columbia University, George Crocker Special Research Fund, 

 F. C. Wood, Director.] 



The association of sarcoma of the liver of rats with Cysticercus 

 fasciolaris, the larval stage of Tenia crassicollis of the cat, has 

 been noted by a number of investigators, including two of the 

 present authors; but to our knowledge no one has hitherto reported 

 the experimental production of tumors by the employment of 

 this parasite as an agent. The purpose of the present note is to 

 record several cases of sarcoma of the liver in a group of 500 rats 

 infested with the Cysticercus by feeding the animals eggs of the 

 Tenia obtained from cat feces. Two hundred and fifty of these 

 rats were alive when the first tumor was discovered, and 170 are 

 still under observation. 



Large tumors were discovered in the livers of four rats, 296 

 to 357 days after feeding. In each case the tumor originated 



1 E. M. Landis announces in the current number of the American Naturalist, 

 Vol. 54, pp. 453-57, the discovery of an amicronucleate race of Paramecium cau- 

 datum. 



