AN AMICRONUCLEATE OXYTRICHA 475 



Part I. 1. Study of the normal animal with attempts to 

 induce conjugation. 2. Cannibalism. 

 Part II. The formation of double animals or 'twins.' 



I take pleasure in acknowledging my great indebtedness to 

 Prof. Lorande L. Woodruff, at whose suggestion this investi- 

 gation was begun, for his advice and criticism throughout the 

 entire course of this study. I also wish to express my thanks to 

 Prof. Alexander Petrunkevitch for assistance in making the 

 microphotographs and to Dr. Rhoda Erdmann for valuable 

 suggestions in technique. 



2. MATERIAL AND METHODS 



The hypotrich used for these experiments was obtained orig- 

 inally in the fall of 1915 in some debris, from a pond in the 

 vicinity of New Haven, which had been placed in a laboratory 

 aquarium. A pedigreed culture was carried from February 22 

 to June 21, 1916, when it was discontinued. Since this time 

 stock from the same culture has been in the laboratory aquaria, 

 and an individual of this species which was isolated from an 

 aquarium in the • Osborn Zoological Laboratory on July 10, 

 1917, has supplied all the animals used in this experimental 

 study. 



The species has been found to agree very closely with the 

 description given by Stokes ('88) for Oxytricha hymenostoma. 

 Systematic works do not usually describe specifically the macro- 

 nucleus or micronucleus, more stress being laid on the external 

 structures for classification. As the absence of a micronucleus 

 and the slight differences shown by this form from Oxytricha 

 hymenostoma Stokes were not assumed to be of specific value, no 

 attempt is at present made to establish a new species, the hypo- 

 trich being identified provisionally as Oxytricha hymenostoma. 



On July 11th the animal, which was isolated on the previous 

 day, had divided twice, and the four resulting organisms were 

 isolated On depression slides in about five drops of culture medium 

 to form the four lines of culture A. In this culture and in all 



