182 Recent Literature. [April 



Cambridge, qitisciila and (enetis completely intergrade, (5) This inter- 

 gradation is in every instance accomplished through phase No. 3 of 

 quiscula." 



From his measurements Mr. Chapman concludes that "the difterences 

 in size, which exist between these three forms, are too slight to be of 

 diagnostic value in individual cases, the range of variation in either form 

 completely overlapping the average differences." 



"J^uiscaius cvneus presents slight but regular increase in size northward 

 .... On the whole it appears to be a somewhat smaller bird than quis.- 

 ciila, with perhaps a slightly longer tarsus." 



"In a<rlcBus and quiscula, in passing from the South northward we find 

 about the same increase in size shown by (Tneus; the wing and tail become 

 longer, the bill thicker, but the length of this member decreases; Florida 

 specimens having an actually, as well as relatively, longer bill than 

 northern specimens." 



The author seeks an explanation of the intergradation from lei/eics into 

 quiscida, and finds it, to his own satisfaction, by assuming that it is due 

 to hvbridity between two distinct species. That it is a case of geograph- 

 ical variation he considers impossible, for, he says, we know of no differ- 

 ences of environment between the regions inhabited by the two forms, 

 sufficient to cause the differences between them, and he thinks further 

 that it is contrary to known laws of geographical variation for a form to 

 continue as constant as ceneiis throughout a wide area and then abruptly 

 change into one as different as quiscula. 



It appears almost as if he had overlooked what certainly seems to be the 

 simplest explanation of the facts, — that it is a case of geographical inter- 

 gradation between two subspecies, one, aglceus, inhabiting the peninsula 

 of Florida and the adjacent coasts, the other, (cneus.. spread over a large 

 area in the West and North; between them a gradual intergradation from 

 one into the other, every step of which Mr. Chapman has shown us in his 

 'phases' 'No. 2' and 'No. 3' and the many specimens intermediate between 

 them. From this point of view the greater part of the series he calls 

 quiscula — all, indeed, that are usually called by that name — are to be 

 considered as intermediates of varying degree between the two subspecies 

 aglccus and ceneus, each of which, within its own territory is as constant 

 as a subspecies can be fairly expected to be. 



If we resort to the theory of hybridity between aneus and quiscula which 

 he is inclined to accept, our way is not without stumbling blocks. Ac- 

 cording to this view the cEtieus blood has mingled in the veins of quiscula 

 to a greater or less degree the nearer or farther from the habitat of ccneus 

 the impure quiscula is bred. But why should this corruption of the quis- 

 cula stock have penetrated nearly the whole of the area the bird occupies, 

 while the territory of (cneus has not been invaded at all by the other.'' If 

 hybridization had gone on to such an extent we should expect to see at 

 least some traces of quiscula blood cropping out now and then through 

 the wide range of country that aneus inhabits. But such mongrels do not 

 appear. — C. F. B. 



