522 



SCIENCE. 



[N. S. Vol. XIV. No. 353. 



By molecular motion is meant, " the trans- 

 latory motion of the centroid of the atoms 

 that form the molecule, while as atomic 

 motion we count all the motions which the 

 atoms can individually execute without 

 breaking up the molecule. Atomic motion 

 includes, therefore, not only the oscillations 

 that take place within the molecule, but 

 also the rotation of the atoms about the 

 centroid of the molecule." * 



Thus it is conceivable that vital activities 

 may also be determined by the kind of 

 motion that takes place in the molecules of 

 what we speak of as living matter. It may 

 be different in kind from some of the 

 motions known to physicists, and it is con- 

 ceivable that life may be the transmission 

 to dead matter, the molecules of which 

 have already a special kind of motion, of a 

 form of motion std generis. 



I offer these remarks with much diffi- 

 dence, and I am well aware that much that 

 I have said may be regarded as purely 

 speculative. They may, however, stimu- 

 late thought, and if they do so they will 

 have served a good purpose, although they 

 may afterwards be assigned to the dust- 

 heap of effete speculations, Meyer writes 

 as follows in the introduction to his great 

 work on ' The Kinetic Theory of Gases,' 

 p. 4 : "It would, however, be a consider- 

 able restriction of investigation to follow 

 out only those laws of nature which have a 

 general application and are free from hy- 

 pothesis ; for mathematical physics has won 

 most of its successes in the opposite way, 

 namely, by starting from an unproved and 

 unprovable, but probable, hypothesis, ana- 

 lytically following out its consequences in 

 every direction, and determining its value 

 by comparison of these conclusions with 

 the result of experiment. " 



John G. McKendrick. 



University of Glasgow. 



* Meyer, 'Kinetic Theory of Gases.' Translated 

 by Baynes, London, 1899, p. 6. 



DATA ON SONG IN BIRDS. OBSERVATIONS 



ON THE SONG OF BALTI3I0RE ORIOLES 



IN CAPTIVITY. 



Much has been written in regard to the 

 songs of birds, and no small part of the 

 literature of the subject has dealt with the 

 problem of the way in which many kinds 

 of birds have acquired the distinctive song 

 that characterizes each different species. 



In the eastern United States many of us 

 recognize, without seeing, the singer, on 

 hearing the song of one of our commoner 

 native birds. We say, ' A robin is sing- 

 ing,' 'Listen to the bobolink,' 'That is a 

 song sparrow.' 



Some who pay close and particular atten- 

 tion realize that individuals of a given kind 

 have sometimes slight, though marked, 

 variations in the method of song that dis- 

 tinguish them from the mass of their kind 

 and characterize them as individuals which 

 are readily known by their peculiar personal 

 song. So we say, ' This robin is a good 

 singer, ' ' The note of that thrush is par- 

 ticularly pleasing,' ' That oriole has some 

 harsh notes.' Such comments are indica- 

 tive of the taste or appreciation of the 

 listener and are only introduced here to 

 emphasize two facts. First, that the song 

 of all the individuals of a given kind of 

 bird, as the robins, is so characteristic that 

 we call it the robin's song, readily recognize 

 it, and know that, in the main, all the 

 robins of a given region have a common 

 song, so much alike that we do not indi- 

 vidualize the singer. Second, that now and 

 again individual birds of a given kind, robins 

 again for example, are readily distinguish- 

 able as individuals by some turn or phras- 

 ing of the notes that gives to the individual 

 singer an identity as a particular robin, 

 with an individual song, different, to a 

 greater or less degree, from the mass of 

 robins in the same region. 



The question at once suggests itself: 

 How is this characteristic song acquired ? 



