ISol.] 175 



Now we have here the extraordinary fact, that while the native population in 

 the thirty-one districts is represented to be nearly 15,000, the whole number of 

 half-castes or mulattoes does not exceed 200. 



The causes of this singular disparity have been variously surmised. Infanti- 

 cide at birth is one of them ; but this can have but a partial effect, for we find 

 that fully one-half of the mixed race is living with the natives. Syphilis is also 

 adduced, but its influence is manifestly very restricted. Promisaions inter- 

 conrse is certainly a check upon fecundity ; but why should its influence be more 

 manifest in Australia than elsewhere ? and as to repugnance between the races, 

 this has been set aside by local circumstances. These and various other con- 

 siderations have been cited in explanation, but without satisfying the inquirer ; 

 and we may therefore ask, is not the real cause the difference of race, the dis- 

 parity of primordial organization ? 



Perhaps no two human races are more remote from each other than the Eu- 

 ropean and Australian ; and where such extremes are blended, reason and analogy 

 lead u? fo expect only a limited fertility. In connection with, and explanatory 

 of, this phenomenon, Count Strzelecki, a distinguished Polish traveller, has 

 stated the following proposition, which I give nearly in his own terms: When- 

 ever a female of an aboriginal or barbarous tribe, has conceived by a European, 

 she loses the power of conception on a renewal of intercourse with a male of her 

 own race, retaining that only of procreating with a white man. "Hundreds of 

 instances of this extraordinary fact," observes Count Strzelecki, "are on record 

 in the writer's memoranda, to prove that the sterility of the female being relative 

 only to one, and not to another male, is not accidental, but follows laws as cogent, 

 though as mysterious, as the rest of those connected with generation." New 

 South Wales and Van Diemen''s La7id, p. 34G. 



My object on the present occasion is merely to state the apparent facts of the 

 case, in order to draw the attention of physiologists, and observers in general, to 

 a more careful and extended notice of these remarkable phenomena. 



April 29th. 

 Dr. Morton, President, in the Chair. 



The Committee to which was referred Mr. Cassin's paper read at 

 last meeting, reported in favor of publication in the Proceedings. 



Notes of an examination of the Birds composing the family Caprimnlgidce., in 

 the collection of the Academy of Natural Sciences of rhiladelphia. 



By John Cassin. 



1 . Caprim. u Igidm . 



No family of birds presents an aspect more uninviting, nor perhaps greater 

 real difliculties in its investigation, nor has any one been more generally neglec- 

 ted, than this. The great fathers of modern Zoology have been but rarely con- 

 sulted respecting their knowledge of Caprimulgus. 



The notes I am now about to offer, I have only to say, are the results of much 

 labor and of as careful research as I am capable of making, with the assistance and 



