Brewster.] 404 [October 3, 



so well known? Before attempting to answer this question I 

 must again refer to the experience of our expedition. 



A number of Wilson's Petrels, shot at various times and places 

 between the dates June 17 and July 25, were carefully dissected 

 with a view to ascertaining their time of breeding. With all the 

 condition of the sexual organs was similar ; viz., at the very low- 

 est stage of erotic development. The testes of the males were 

 scarcely larger than dust shot, while the ovaries of the females 

 presented the appearance of whitish sacs in which the separate 

 ovules could not be clearly seen without the aid of a glass. I ex- 

 amined the females for signs of recent ovulation or incubation, 

 but could find none. Furthermore, a male, taken June 18, showed 

 every indication of being a young bird about eight or ten weeks 

 from the nest. Its plumage differed appreciably from that of 

 some adults shot the same day, and its skull and bones were very 

 soft, the skull having that flexible, skin-like character found only 

 in young birds. 



These facts confirm a suspicion which I have entertained for a 

 long time ; viz., that Wilson's Petrel breeds in winter or early 

 spring in tropical or sub-tropical regions and visits the coast of the 

 north-eastern United States only in the interim between one breed- 

 ing-season and the next. In support of this theory are the follow- 

 ing facts : (1) That although the bird literally swarms off our 

 coast during June, July, and August no one has ever found it 

 breeding on the neighboring shores. (2) That the sexual organs 

 of numerous summer specimens which I have dissected have been 

 invariably undeveloped. (3) That a specimen taken June 18, 

 although apparently a young bird, was at least two months old, 

 thus indicating a date of breeding when the species is not to be 

 found in our waters. If the above conclusions prove correct the 

 case, as far as we now know, will be unique. But there are reasons 

 for suspecting that the same thing obtains with other North Amer- 

 ican Procellaridae, especially our two common species of Puninus. 



83. Pufiinus major, Faber. - Greater Shearwater. 



We saw no Shearwaters in the Gulf, but the present species was 

 met with off the Nova Scotia coast on June 19 and 20, and again 

 near Mt. Desert during the return voyage in August. It was 

 nowhere very numerous, only a few individuals being seen in any 

 one day and these at wide intervals. They were less familiar than 



