RECORDS. 187 



Knight under the direction of the speaker with the assistance 

 of other members of the department. Numerous models and 

 drawings were exhibited and described. Of special interest 

 were the following : Elcplias imperiales (Imperial mammoth) ; 

 Trilop]iodo7i prodiictiis (Miocene mastodon) ; and Icthyasaurus 

 and young ; several Pleistocene rhinoceroses ; and Diplodociis 

 (a bird-catching dinosaur). 



Professor Thorndike reported a study of the size of families 

 of college graduates during the nineteenth century and of the 

 descendants of a New England family during the eigthteenth and 

 nineteenth centuries. The average number of children in the 

 latter case rose gradually to an acme in the generation born about 

 1720 and then fell steadily, the figures for eight generations being 

 5-3> 6-3. 7 -7 y lo.o, 7.2, 5.5, 4.4, 3.8. This rise is inconsistent 

 with the common hypothesis that social custom is the cause of 

 change in the productivity of races. So also is the form of the 

 surface of frequency of family size in the later decades of the 

 nineteenth century (see Popular Science Montldy, May, 1903, p. 

 68). A real decrease in natural fertility would account per- 

 fectly for the statistical appearances found; and, if we judge 

 only by them, is the most likely hypothesis. 



Mr. Brues presented a preliminary account of " The internal 

 factors of Regeneration and Reversal of Asymmetry in the crus- 

 tacean AlpJieus.'" Przibram and Wilson have recently shown 

 that when the larger of the asymmetrical chelae of these ani- 

 mals is amputated, the smaller one on the opposite side 

 develops into a claw of the large type while a small one regen- 

 erates on the stump of the large one. If the nerve of the 

 small claw be severed at the time of removing the large one, re- 

 versal does not take place, or only incompletely. Histological 

 examination of animals in which such changes are taking place 

 indicates that the regeneration and remodeling are influenced 

 by the nervous system, due possibly to increased nutrition in 

 the ganglion which supplies the small chela. As the nervous 

 system shows no morphological asymmetry corresponding to 

 that of the claws, it propably acts only in a passive way in de- 

 termining the type of the claw, although it evidently gives the 



