86 Records of the Indian Museum. [Voi,. Ill, 



contain one or two pure black rats and four or five others of a 

 blackish tone which show a varial)le mixture of brown hairs; but 

 one cannot find, when dealing with hundreds, every shade betw^een 

 a black rat and a light brown one. Similarly, one cannot arrange a 

 satisfactory- series between the white-bellied type and the commoner 

 brown-bellied type, although some of the former have coloured 

 breast stripes of variable breadth and some of the latter are very 

 light in colour. 



The collection is truh' heterogeneous in appearance, although, 

 in a broad sense, it consists of animals of one species. The indivi- 

 duals composing it have been brought in batches of two or three 

 together, by the townsfolk. It is often noticeable that the in- 

 dividuals of any one batch very closely- resemble one another. 

 Thus the melanotic and semi-melanotic rats would probably all be 

 brought in by one man. Another man would bring unusually large 

 rats, a third would bring four or five white-bellied rats with rela- 

 tively short tails, some with breast stripes, others without. The 

 members of the separate batches often show a likeness to one 

 another. This can only be explained b}' the fact that the members 

 of each batch were usually taken together from a single house, the 

 likeness being a true " famil}^ likeness." B3' the word " family " 

 is meant a small localized group whose members are given to in- 

 breeding. These observations point to the conclusion that the 

 rats of one species in a town are divided into a number of groups 

 which hold little intercourse with one another. 



Experimental evidence of a more certain nature could be 

 obtained b}- successively capturing, marking, releasing, and after 

 an interval recapturing a large number of rats. It might be pre- 

 dicted that the recapture would take place in all cases in the same 

 house that the capture and marking was effected. Such experiments 

 could probably be carried out without much difficulty. The rats 

 should be caught in a trap, anaesthetized lighth* by placing the 

 traps in a closed box containing chloroform, and removed from the 

 trap while' unconscious. The}' might be marked b}' branding the 

 tail or piercing the ears. Recovery from chloroform in rats takes 

 place with certainty, and often with most disconcerting quickness. 

 The accidental scars which are present on so man}' rats might lead 

 to some confusion, but a system of marking by metal rings and 

 number plates would probably prove unsatisfactory. To recapture 

 the rats it would be probably necessar}' to use spring jaw traps of 

 which there are man}' effective patterns. Such experiments would 

 give direct evidence of the movements of rats in a town or village 

 which would be of value in any consideration of the means of plague 

 dissemination. 



APPENDIX II. 



Questions of Bioi^ogical Interest. 



The Government's measures against rats have afforded a 

 unique opportunity of studying large numbers of closely related 



