564 SCIENCE PROGRESS. 



referred to by Standfuss ({8), p. 307), in crossing the 

 varieties of Spilosonm lubricipeda and the results obtained 

 by several observers in this country working with the same 

 species. It is well known to entomologists that of this 

 species there is a peculiar dark form, zatima. Cram, found 

 in Heligoland. ^ 



This variety has been observed to breed true when 

 paired (7). Now there is good evidence that when the 

 Heligoland variety is crossed with the type, the offspring 

 may consist of the type, of true zatima, and of certain lighter 

 forms of this variety, named var. intermedia of Bang-Haas. 

 But between this latter variety and the type, though crosses 

 of the most various nature were continued for four years and 

 an immense series of specimens reared, the intermediates 

 were always wanting (8). But this is not because such 

 intermediates cannot exist. In England a dark race of 

 lubricipeda has been artificially reared by selection (start- 

 ing from naturally dark specimens) by the Yorkshire 

 entomologists, which approaches rather nearly to the true* 

 zatima. These artificially produced forms are known as 

 radiata. In a series of them belonging to Mr. Porritt's 

 strain, kindly shown me by Mr. Barrett, are many of 

 both sexes which quite fill up the gap between inter- 

 media and true lubricipeda. Still more completely is this 

 interval filled by a series lent me by Mr. W. H. B. 

 Fletcher, which had been reared by crossing the partially 

 artificial radiata with another variety. 



Again Standfuss records that by crossing the natural 

 dark variety eremita, a form of Psihtra monacha, with the 

 type, a brood was produced containing one female eremita, 

 the rest being all typical monacha. This cross-bred female 

 he again crossed with a male of the type and there resulted 

 twenty-two normal 7iioitacha, twenty-three typical eremita, 

 and six individuals in which the characters of type and 

 variety were asymmetrically mixed. Such a brood is a 

 clear proof of imperfect blending of the two characters. 



^ Whether it is there associated with the type or not I cannot find 

 clearly stated by any authority, but I gather that the normal as well as the 

 variety occurs in the island. 



