HEREDITY OF COAT CHARACTERS IN 

 GUINEA-PIGS AND RABBITS. 



BY W. E. CASTLE. 



INTRODUCTION. 



The experiments to be described in this paper have been in progress 

 in the Zoological Laboratory of Harvard University since the year 1900 . 

 They were begun for the study of conditions governing sex in the higher 

 animals, but have yielded results bearing on certain other questions, 

 which alone will be considered in this paper. 



The animals used, guinea-pigs and rabbits, were selected because of 

 their early maturity and fecundity. To provide them with food and 

 shelter and to give them the necessary daily care, in addition to keep- 

 ing records as full as possible, have been no small task. In this con- 

 nection I am indebted for invaluable assistance to a number of per- 

 sons. First of all to Prof. E. L. Mark, director of the zoological 

 laboratory, without whose encouragement and support the experi- 

 ments could never have been undertaken, and who has more than 

 once come to the rescue when the material resources at my command 

 were exhausted and further progress seemed impossible. The director 

 and other officers of the Museum of Comparative Zoology, and the 

 President of the University, have generously provided quarters for the 

 animals and in other ways have aided the enterprise. Finally, when 

 the increasing cost became a burden too heavy for the laboratory to 

 bear, it was assumed by the Carnegie Institution of Washington in the 

 form of a grant to Professor Mark and myself for experimental studies 

 in heredity. Under the auspices of the Carnegie Institution the work 

 has been in progress since January, 1904, and this paper is presented 

 as a first detailed report upon it. 



In the course of the experiments about 3,000 guinea-pigs and several 

 hundred rabbits have been reared. 



For valuable guinea-pigs and excellent practical suggestions I am 

 indebted to Miss Jeannette Soule, secretary of the National Cavy Club ; 

 for an interesting stock of albino rabbits I am indebted to Prof. R. T. 



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