806 



SCIENCE 



[N. S. Vol. XXXVII. No. 960 



tain V = .0484, a difference of 5 per cent. 

 As a check upon the accuracy of the readings, 

 it will be seen that the differences between the 

 velocities in Cases I. and II. and between 

 those in HI. and IV., representing double the 

 velocity due to the difference in density of the 

 water in different parts of the tube, are about 

 equal; also the differences between Cases I. 

 and III., and II. and IV., representing the 

 variation due to imperfect adjustment of the 

 axis, are approximately the same. In order 

 to show that there was no appreciable effect 

 from convection currents while the ring was 

 in a horizontal position, several readings were 

 taken after the tube had remained at rest for 

 some time, none of which showed a motion 

 larger than .015 mm. per second. 



In order to obtain the best possible results, 

 the ring should be mounted as rigidly as pos- 

 sible in a room of equal temperature through- 

 out, and the axis should be capable of accu- 

 rate adjustment parallel to the ring. If the 

 radius of the ring were made smaller, although 

 the effect of the earth's rotation would be less, 

 it would be easier to keep all parts of the tube 

 at an equal temperature, and the ring could 

 be turned more quickly. Moreover, since the 

 motion would not be so great, the velocity of 

 the water would diminish less rapidly, so that 

 more accurate readings could be obtained. 

 With a more mobile liquid the motion would 

 of course continue longer. Even with the 

 comparatively crude apparatus described 

 above, however, it is not difficult to show 

 that the earth revolves. 



Arthur Holly Compton 



Physical Laboratory, 

 University op Wooster, 

 January 13, 1913 



CROSSOPTERYGIAN ANCESTRY OF THE AMPHIBIA 



Fob many years evidence has been accumu- 

 lating for the view that the Amphibia have 

 been derived not from Dipnoi but from Cros- 

 sopterygians of some sort. Pollard' held that 

 the Amphibia were remotely related to the 



^"On the Anatomy and Phylogenetio Position 

 of Polypterus," Zool. Jahrb. AM. f. Aiiat. u. Ont. 

 (Spengel), V. Bd., Jena, 1892, pp. 387^28, Taf. 

 27-30. 



living Polypterus and Baur" was able to 

 strengthen the evidence, to some extent, from 

 the Stegocephalian side. More recently 

 Thevenin' has es;pressed similar views, while 

 Moodie,' correcting Baur's observations on the 

 lateral line grooves in the skull has seemingly 

 demonstrated the general homology of the 

 skull top of Polypterus with that of Stego- 

 eephalia. Gegenbaur" supported the homology 

 of the Stegocephalian cleithrum with the 

 " clavicle " of Polypterus and other fishes, 

 while Klaatsch" showed that the pectoral 

 limbs of Polypterus both in musculature and 

 osteology in many respects remotely suggest 

 Amphibian conditions. On the other hand, 

 Goodrich's' studies on the scales of fishes, to- 

 gether with the evidence offered especially by 

 the brain of Polypterus, tend to remove that 

 genus widely from genetic relationship with 

 the Amphibia. 



The Paleozoic Crossopterygii have hitherto 

 yielded a few, though significant, hints of 

 Amphibian relationship. The Texas Permian 

 Crossopterygian fish named by Cope Ecto- 

 steorhachis nitidus and recently figured by 

 Hussakof^ as Megalichthys nitidus, suggests 

 remote Stegocephalian affinities in the skull 

 and the same is true of Bhizodopsis, as figured 

 by Traquai/ and of Osteolepis, as figured by 



^ ' ' Les Plus Aneiens Quadrup6des de France, ' ' 

 Annales de Pal. (Boule), tome V., 1910, pp. 1-64, 

 pi. I.-IX. 



■* ' ' The Lateral Line System of Extinct Am- 

 phibia," Journ. of Morphol, Vol. XIX., No. 2, 

 1908, pp. 511-540; 1 pi. 



" ' ' Clavicula imd Cleithrum, ' ' Morplwl. Jahrb., 

 XXIII. Bd., Leipzig, 1895, pp. 1-21. 



° ' ' Die Brustflosse der Crossopterygier, ' ' Fest- 

 schr. fur Gegenbaur, I. Bd., 1896, pp. 259-391, 

 Taf. I.-IV. 



^"The Stegocephali. A Phylogenetio Study," 

 Anai. Aug., XI. Bd., 1896, No. 22, pp. 657-673. 



' Cf . Lankester 's ' ' Treatise on Zoology, ' ' Part 

 IX., first fascicle. ' ' Cyolostomes and Fishes, ' ' by 

 E. S. Goodrich, 1909, especially pp. 217-219, 290- 

 300. 



'"The Permian Fishes of North America," 

 Publ. No. 146 Carnegie Institution of Washington, 

 pp. 168 and pis. 30, 31. 



°"0n the Cranial Osteology of BJiisodopsis," 

 Trails. Soy. Soc. Edinburgh, Vol. XXX., 1881. 



