382 CARNEGIE INSTITUTION OF WASHINGTON. 



ZOOLOGY. 



Castle, W. E., Harvard University, Cambridge, Massachusetts. Continuation 

 of experimental studies of heredity in small mammals. (For previous re- 

 ports see Year Books Nos. 3-12.) 



The problems upon which my studies are centered and the methods 

 adopted for attacking them were so fully outhned in Year Book No. 

 12 that I shall confine myself in the present report to stating the 

 progress which has since been made. As then reported, several ex- 

 tended investigations had reached a point warranting full publication. 

 Accordingly the past year has seen greater activity than usual in this 

 direction. PubHcations No. 195 and 196 have been issued. Dr. Det- 

 lefsen's work on guinea-pig hybrids is in process of publication, and 

 fifteen shorter papers have been published by Drs. Little, MacDowell, 

 Phillips, and myself, deahng with or closely related to the work carried 

 out under this grant. 



New work undertaken relates chiefly to the stocks of guinea-pigs, 

 wild, feral, and domesticated, obtained from Peru in the expedition 

 of 1911. In this I am being assisted by Mr. S. Wright. This material 

 is yielding interesting results, among which may be mentioned the 

 discovery of color stages intermediate between the pigmentation of 

 ordinary mammals and albinos, all of which fall into a single series 

 of allelomorphs. It is a good illustration of what Bateson has called 

 fractionation of a Mendelian character. 



Dr. Phillips having, during the past year, been absent on zoological 

 expeditions or engaged in extensive breeding experiments with ducks 

 and pheasants at his home, has been unable to give further attention 

 to the breeding experiments with rats which we had carried on jointly 

 for several years. Accordingly I have made the rat experiments my 

 own immediate and principal object of study. New all-metal cages 

 have been installed and the feeding and caretaking have been simplified 

 •and systematized. In attempting to devise a standard ration for 

 laboratory rats, I have had valuable assistance from Professors 

 Osborne and Mendel. 



Riddle, Oscar, Cold Spring Harbor, Long Island, New York. Preparation for 

 publication of the manuscripts of the late Dr. C. 0. Whitman, provision 

 for care and maintenance of the Whitman pigeon collection, and continuation 

 of investigations necessary for completioji of Dr. Whitman's manuscripts. 

 (For previous reports see Year Books Nos. 11, 12.) 



During the year a large part of Professor Whitman's data on breeding 

 and sex, and on ''strength" and "weakness" of germ-cells, have been 

 summarized, tabulated, and made ready for publication. This work 

 has required the repeated inspection of the entire body of records and 

 manuscripts. The manuscripts on "behavior," in the hands of Pro- 



