1868.] 85 [Allon. 



then return to the surface and blo^v from tAventy to fifty times, during 

 which time the top of their backs may Ije seen above the water. If 

 tliey are harpooned when they first come to the surface they are killed 

 witli but little trouble, sometimes going but a few fathoms below tlie 

 surface, but if they are harpooned after having spouted several times, 

 they are apt to go down before they can be killed. Captain Atwood 

 stated that he had been engaged in killing a large sperm whale which 

 went down seven times, each time with more tlian four hundred 

 fathoms of line. 



The Secretary read a paper by Mr. J. A, Allen, upon the 

 birds of Iowa and Illinois, in which the author discussed 

 some points connected with the migrations of these animals. 



Mr. Allen believed that the geographical limits of the diflferent prov- 

 inces and faunae among birds must be based upon their i*ange during 

 breeding season ; at other times migratory birds are rarely localized 

 for any considerable period and cannot be termed inhabitants of a 

 region through which they merely pass; even where they do re- 

 main for a short time, a species is represented, not by the same 

 individuals, but by a succession of earlier and later birds. Migrations 

 consist of a general swaying to and fro of all the representatives 

 of a species — southward in winter and northward in summer; 

 those birds whose limits of migration are the most extended pass 

 nearly two-thirds of their lives in journeying, seldom pausing, ex- 

 cept in the breeding season, for long intervals, but beginning slowly 

 to retrace their steps almost as soon as they have reached their 

 southern limits; their breeding country is their only true home. 



We need therefore something more than bare catalogues of the spe- 

 cies which occur in any lo(!ality to determine the laws which regulate 

 the distribution of birds. Dana, Forbes, and others, have pointed 

 out how greatly the distribution of marine animals depends on tem- 

 perature. Verrill has also shown the close coincidence of the bound- 

 aries of some faunje with the lines of equal mean temperature for the 

 months of April, May and June; other influences, such as humidity 

 and vegetation, have, of course, their place, but these, too, are plainly 

 the result of climatic causes. A comparison of the birds breeding 

 in the Alleghanian fauna with those in the Canadiiin and Louisianian 

 fauns', shows that the Alleghanian diifers from the others in having 

 few. if any species., peculiarly its own. thus forming, as it were, a 

 transitional ground. Here, too, as we pass northward, we notice 

 more conspicuously that the species fade out at frequent intervals. 



