NOTES AND LITERATUEE 



WORK ON GENETIC PROBLEMS IN PROTOZOA 

 AT YALE 



Two ideals are commonly represented in the practise of uni- 

 versity laboratories. Some concentrate upon a unified set of 

 problems, endeavoring thus to make a definite mark upon science ; 

 others cultivate breadth, the different workers taking up prob- 

 lems lying in diverse fields. The work done in recent years at 

 the Yale Zoological Laboratory by Professor L. L. "Woodruff 

 and his associates is an interesting example of the former type ; 

 the present is an attempt to give a unified survey of this work, 

 which has been directed with concentration and effectiveness 

 upon the general questions of reproduction in unicellular animals. 



The work on these matters may be represented as a tree with a 

 single trunk and diverging branches. The trunk consists of the 

 study of Woodruff's culture of a single line of Paramecium, 

 begun in 1907, to test the hypothesis that death is a necessary 

 consequence of continued reproduction without conjugation. 

 This study was itself an outgrowth of an investigation (the seed 

 of the tree) made by Woodruff as a student under the direction 

 of the investigator who has been chiefly responsible for the recent 

 revival of work on the more general problems of reproduction in 

 the Protozoa, Professor Calkins, of Columbia University. This 

 first investigation (1) led to results in agreement with the views 

 of Maupas and of Calkins, that continued reproduction without 

 conjugation results inevitably in death. 



All the cultures give incontestable proof that the species studied 

 [Oxytricha fallax, Pleurotricha lanceolata, and Gastrosttjla steinu] pass 

 through cyclical periods of general vitality. The periods of depression 

 lead to death if the culture is subjected to the same environment. 

 Minor fluctuations also occur which may be called "rhythms." 



A rhythm is a minor periodic rise and fall of the fission rate, due 

 to some unknown factor in cell metabolism, from which recovery is 



A cycle is a periodic rise and fall ot' the lis>ion rate, extending over a 



unless it is "rejuvenated" hv conjugation or changed environment 

 (1, page 627). 



Woodruff, however, felt that the matter needed further test, 

 particularly with relation to the part played by environmental 

 434 



