446 Mr. G. A. K. Marshall on 



Very careful and numerous records over a large number 

 of years would be required to show that any change in the 

 relative time limits of the two forms is taking place. 



Owing to the kindness of Mr. S. L. Hinde, H. M. Sub- 

 Commissioner, East African Protectorate, and Mrs. Hinde, 

 I have received a most interesting series of the two forms 

 from British East Africa, probably near the northern 

 boundary of the range of the species. The numbers, 

 captured in a short time on a limited area, are sufficient 

 to enable us to judge of the relative proportions of the 

 two forms, and we see that in May and the beginning of 

 June the two occur mixed in about equal proportions, 

 while in December and January the wet phase greatly 

 predominates, although an occasional dry form appears, as 

 it does in Mashonaland, early in January. I have included 

 in the series two other specimens from near the northern 

 part of the range of P. scsamus. The whole list is wonder- 

 fully similar to that from Mashonaland, and supports the 

 view that Mr. Marshall's observations record the normal 

 mode of replacement of the wet by the dry phase, although 

 the former persists in large numbers much later in the 

 north than it does in the south. 



