00 BIOLOGICAL SOCIETY OF WASHINGTON. 



environment growing gradually less and less favorable, but not 

 the less adapted to display in a very clear light some of the 

 most important laws of transformation. 



In 1877 Mr. John A. Ryder read a paper "On the laws of 

 digital reduction,"* showing the obvious adaptations to the 

 changing environment which had taken place in vertebrates 

 in this respect, and a year later he pursued the same line of 

 argument for modifications of the teeth, f 



Mr. Ryder has for many years past been engaged in embry- 

 ological researches, but there is no evidence that they have 

 led him to abandon the views expressed in these earlier papers 

 in favor of those of Weismann. On the contrary, several 

 comparatively recent papers of his J consist in great part of 

 direct attacks upon Weismann' s teachings and criticisms of his 

 embryological theories. 



Professor Cope commenced publishing on this subject at 

 about the same time and has continued to study the vertebrate 

 fauna of America without interruption to the present time. 

 It appeared to him from the first that paleontology affords 

 proof of the causes of variation, as revealed in the wonder 

 fully complete transition series that are found in the teeth, 

 toes, and various parts of the skeleton of extinct animals, 

 adapting them to a changing environment and higher struc 

 tural perfection. The study of living animals cannot, in the 

 nature of things afford any such series of forms, and the evi- 



* American Naturalist, Vol. XI, October, 1877, pp. 603-607. 



f On the mechanical genesis of tooth forms, by John A. Ryder. 

 Proc. Nat. Sci. Phil., Vol. XXX, 1378, p. 45 ; Vol. XXXI, 1879, p. 47. 



J The Origin of Sex through Cumulative Integration and the Relation 

 of Sexuality to the Genesis of Species. Proc. Am. Phil. Soc., Vol. 

 XXVIII, May 29, 1890, pp. 109-159. 



A Physiological Hypothesis of Heredity and Variation. Am. Nat, 

 Vol. XXIV, January, 1890, pp. 85-92. 



