Januaev 17, 1902.] 



SCIENCE. 



109 



had, and it seems to me worth while to state 

 what conclusions my studies have led me to. 



No group of birds with which I ami ac- 

 quainted shows such remarkable uniformity 

 in their pterylography as do the humming- 

 birds. So far as I can see Professor Thomp- 

 son's figures of Patagona would answer, al- 

 most without change, for any of the 11 species 

 I have examined. The only important differ- 

 ■ence is the absence of anything like what he 

 calls the 'lateral' tract; I have found this in 

 none of the specimens before me. In the 

 feathering of the occipital region, moreover, 

 my specimens do not agree with his figure, 

 though they answer well to his description. 

 Even nestlings and embryos (removed from 

 the egg before hatching) of Mellisuga have 

 precisely the same pattern of pterylosis, as in 

 all adults. The swifts are not so constant to 

 a single pattern as the hummers, and show 

 some considerable generic diversity, but they 

 nevertheless possess a very characteristic tj-pe 

 of pterylosis. I am utterly unable to agree 

 (however much we may allow for individual 

 diversity in the birds and the personal equa- 

 tion of the observer) to either Dr. Shufeldt's 

 account, or Professor Thompson's figure, of 

 the cypseline pterylosis. This is not the place 

 to enter into details, but one point at least 

 must be mentioned. The posterior cervical 

 apterium, so conspicuous in the humming- 

 birds, is present in every swift I have ex- 

 amined, and I have not seen it in any other 

 birds. Professor Thompson failed to find it 

 in Collocalia and Dr. Shufeldt says it is never 

 present in the swifts ! 



In the feathering of the head, the humming- 

 birds do show a slight resemblance to the goat- 

 suckers, but this is really not so close as ap- 

 pears at first sight. The swifts difEer from 

 both, but some species have the feathers on 

 the occiput few and far between, as in the 

 hummers. It must be borne in mind, however, 

 that the pterylosis of the head is quite vari- 

 able, perhaps more so than that of any other 

 part of the body. In the pterylosis of the 

 neck, the swifts and humming-birds are very 

 similar, especially on the upper side, while the 

 goat-suckers are strikingly different. The 

 feathering of the back shows considerable re- 



semblance between swifts and humming-birds, 

 for while some swifts have the femoral tracts 

 separate, others have them more or less united 

 with the dorsal, as they are in the humming- 

 birds. The dorsal tract of the Caprimulgi is 

 obviously different, and the femorals are al- 

 ways well defined and free from the dorsal. 

 The humeral tracts in both swifts and hum- 

 mers are near the dorsal, and their posterior 

 ends tend to run into either the dorsal or the 

 anterior end of the femorals. In the goat- 

 suckers, the humerals are narrow and some 

 distance from the dorsals. On the ventral 

 side, we find the sternal tracts in the goat- 

 suckers are more or less abruptly narrowed to 

 form the rather long ventrals, while in the 

 swifts and the humming-birds, the sternals 

 pass imperceptibly into the short ventrals. As 

 far as the number of secondaries is concerned, 

 that is chiefly a matter of size ; humming-birds 

 have 5-7, swifts 8-11, and goat-suckers 12-14. 



Por these, and very similar reasons, I am 

 led to disagree with Professor Thompson that 

 the humming-birds are nearer to the goat- 

 suckers than to the swifts, and I must dissent 

 quite as strongly from Dr. Shufeldt's opinion 

 that the pteryloses of swifts and hununing- 

 birds are 'essentially different.' To my mind, 

 the swifts and humming-birds are pterylo- 

 graphically nearer each other than are grouse 

 and guans, and almost as nearly allied as 

 grouse and quail. I cannot see that the 

 Caprimulgi have any close relationship to 

 either. 



Hubert Lyman Clark. 



Olivet, Mich., 

 October 30, 1901. 



INJURIES TO THE EYE CAUSED BY INTENSE LIGHT. 



There may be some general interest in the 

 following cases of optical phenomena brought 

 about by exposure of the eye to intense light. 



Professor M., while working in a rather dark 

 corner of his laboratory, accidentally broke a 

 low-resistance circuit in which an electric cur- 

 rent at a pressure of five hundred volts was 

 flowing. The arc formed was about a foot 

 from his eyes and appeared like a ball of fire 

 rather more than six inches in diameter. Im- 

 mediately there was a feeling that something 

 had 'given way' in his right eye, though no 



