362 Ml'. 'PonMon's farther experiments upon 



to quote the description of the varieties of this pupa from 

 my earUer paper : — 

 "(1) Very unusually dark, almost black; very little 

 gold, or none. 



(2) Dark normal form ; dark grey, often with a slight 



pinkish tinge, with very little gold, or none. 



(3) Light normal form ; light grey, often with a pro- 



nounced pinkish tinge; more gold than (2), 

 occasionally none, 



(4) Lighter than (3) ; the pinkish tinge often very 



pronounced, and usually a large amount of gold. 

 (•5) Very light forms ; generally completely covered 

 with gold" (Phil. Trans., B., 1887, p. 320). 

 It was also found convenient to subdivide the (3)s still 

 further into dark (3)s, (3)s, and light (3)s. This ar- 

 rangement will be adopted in the present paper. 



Experiments 1 and la. 



A small company of 44 larvae of Vanessa urtica were 

 found at Oxford, at 7.30 p.m., July 11, 1887. They were 

 so obviously mature that it was probable that some had 

 already left the food-plant, and that the shock of capture 

 would cause these remaining larvae also to seek pupation. 

 Their size being very uniform, they were well suited for 

 the purposes of this enquiry. 



About 10 p.m. they were offered food ; the majority 

 refused it, and wandered. These were separated, and 

 again offered food ; and it was assumed that the 29 

 larvae which again refused it, had entered Stage I. of the 

 period before pupation. They were therefore divided 

 between the 3 receptacles described below, while the 15 

 which remained on the food were placed with leaves in 

 3 similar receptacles. The arrangements were complete 

 about 10.45 p.m. 



{See Table, pages 363, 364.) 



Several very interesting conclusions can be derived 

 from this table. 



Bearing upon tJie duration of the stages before pupation : — 



The observations were repeated so frequently that the 

 beginnings of the stages can be fixed with a very small 

 margin of error, 



