ZOOI^OGY — PEARL. 285 



Pearl, Raymond, University of Michigan, Ann Arbor, Michigan. 

 Grant No. 266. Investigation by statistical methods of correlation in 

 variation. (For first report see Year Book No. 3, p. 140.) $1,250. 



Abstract of Report. — During the year the work has been carried 

 forward mainly on the following lines : 



(a) Variation and correlation in Ceratophyllum. An extensive 

 series of material on this form, affording data on the problems (i) va- 

 riation withia the individual organism, and (2 geographical varia- 

 tion, has been collected and almost completely reduced. The laws of 

 growth of the plant have been especially studied and the facts regard- 

 ing the relation of the variation to these laws worked out. 



{b) Correlation in the crayfish, with special reference to morpho- 

 logical factors. The reduction of the material on the crayfish has 

 been completed and a preliminary paper is now in press. 



{c) The effect of environmental changes of known quality and 

 intensity on variation and correlation in the Protozoa. Measure- 

 ments of over 6,000 individual Paramecia, reared under controlled 

 conditions and in pure strains, have now been collected and partially 

 reduced. For purposes of comparison data have been collected from 

 other Protozoa, especially Chilomonas. A preliminary paper is now 

 in press. 



{d) Variation and correlation in various characters of two species 

 of fish, Coregonus clupeiforniis and Stizostedion vitreum. Work on the 

 reduction of this material, comprising something over 30,000 meas- 

 urements of a variety of specific and non-specific characters in these 

 two teleosts, is being carried on as rapidly as possible. The material 

 was collected with special reference to a study of correlation in 

 variation. 



(<?) The correlation between the same and different characters in the 

 individuals of conjugating pairs of Paramecia. The work on this 

 problem has been very successful. After many trials it has been pos- 

 sible to obtain abundant material of conjugating Paramecia and keep 

 it under experimental conditions. It has now been conclusively 

 demonstrated (i) that the two individuals of a conjugating pair of 

 Paramecia are relatively very highly correlated with one another in 

 respect to size (coefficient of correlation >o.5), and (2) that the 

 portion of the Paramecimti population in a given culture which does 

 the conjugating is distinctly differentiated from the non-conjugating 

 portion of the population living in the same culture at the same time, 

 in respect to both size and variability. A preliminary paper on this 

 work has already been published, and the complete paper will be sub- 

 mitted for publication very shortly. 



