THE WHALEBONE WHALES OF THE WESTERN NORTH ATLANTIC. 207 



very probable, but on account of the great amount of individual variation among 

 cetaceans it would be an almost hopeless task to recognize and characterize them 

 without a wealth of material which no museum in the world possesses to-day. 

 To bring together a hundred or a thousand specimens of mice or sparrows side by 

 side for comparison is an easy task, but to accomplish the same for the huge whale- 

 bone whales is almost beyond the bounds of possibility. To say nothing of me- 

 chanical difficulties, the expense involved would be prohibitive. 



The most that the cetologist can hope to do is by collating notes upon, and 

 measurements, photographs, and drawings of, such specimens as can be found at the 

 whaling stations and in museums, to detect constant differences of considerable 

 magnitude. These differences will form the basis of his species. Beyond this he 

 can scarcely go, with any feeling of certainty. 



The importance of the bearing of these considerations on the questions of 

 geographical distribution cannot be ignored, and it may be thought that they impair 

 the usefulness of the present inquiry, for it is a well-known fact that among 

 migratory species groups of individuals presenting but slight differences may follow 

 quite different routes of migration and occupy quite widely separated stations. 



There is no doubt much force in criticism along this line, and it should put the 

 cetologist on his guard against relying too' implicitly upon the results of the rather 

 crude methods which alone are open to him in systematic work. Nevertheless, 

 conclusions as to geographical distribution based on such results, carefully worked 

 out, must certainly have more value than opinions formed on a priori grounds, with- 

 out actual examination of specimens, of which cetology has not been free in times 

 past. Furthermore, examination of even a small number of specimens may lead to 

 the detection of large differences, and so put the question of close relationship out 

 of court. 



The differences between the Greenland and Norwegian skeletons of B. acuto- 

 rostrata which Eschricht finally thought might be of importance were as fol- 

 lows : (1) A slight difference in the position of the dorsal fin, amounting to -fa the 

 total length, as shown in a sketch received by him ; (2) union of the lateral 

 processes of the 5th and 6th cervical vertebrae in the immature skeletons from 

 Greenland, a condition not found by him in Norwegian specimens of more 

 advanced age ; (3) the coronoid process of the mandible " higher, smaller, and 

 more strongly bent outward " in the Greenland skeletons ; and (4) absence of 

 obliquity of the upper jaw in the latter. 



As to the first point, the position of the dorsal fin, it may be said that a 

 variation of -fa of the total length, amounting actually in the case of the Greenland 

 specimen to about 4 inches, is not greater than is found in other species of Balcenop- 

 Ura. In this particular case, however, it is quite as likely that the sketch was 

 slightly inaccurate, as that the variation actually existed. At all events, no stress 

 can be laid on this point under the circumstances. 



The second point brought forward by Eschricht as possibly serving to dis- 

 tinguish the Greenland species was that the specimens though immature and only 

 about 17 or 18 feet long, had the processes of the 5th and 6th cervicals united, 



