K. J. J. Mackbnzik AiNI) F. H. A. Marshall 245 



importance to the investigator who might otherwise be in danger of 

 concluding that certain individual sows belonged to a strain which did 

 not carry mammary pigment, when in reality he would be dealing with 

 cases in which such pigment had formerly been present in (.|uantity and 

 had subsequently been removed. 



The operations were performed at the Field Laboratories, Milton 

 Road, Cambridge, by F. H. A. Marshall. 



The expenses of the investigation were defrayed by the Board of 

 Agriculture and Fisheries out of funds allocated to them for purposes 

 of research, by the Development Commission. 



(Received Juhj 23rd, 1915.) 



