RECORDS OF MEETINGS 295 



spring, and thus selecting germ-cells that would give rise both to long- 

 legged colts and to long-legged adults. The opposite case of divergent 

 evolution between parent and offspring (as in larval adaptations) offers 

 grave difficulties to the Lamarckian hypothesis. 



Convergence and divergence between juvenile and adult structures are 

 well illustrated in a comparison of the milk and permanent dentitions. 

 In many ungulates, the deciduous grinders evolve into a pattern not like 

 that of the teeth which replace them but like that of the true molars. In 

 the European Badger, on the other hand, the milk teeth are totally unlike 

 the true molars. Where the milk molars are much like the replacing 

 teeth, as in the horse, one might almost suspect a direct transmission of 

 new characters from the earlier to the later dentitions ; but this apparent 

 transmission is illusory and so also may be many cases in which juvenile 

 or larval structures resemble those of the parents. 



The speaker then referred to a modernized form of the theory of Nat- 

 ural Selection which had been outlined by Professor T. H. Morgan in 

 Science,^ but left the consideration of this topic to subsequent speakers. 

 In conclusion, he said that no matter by what process convergence and 

 parallelism had been effected, the discovery of these phenomena had 

 already had important effects upon our conceptions of classification and 

 phylogeny. 



Professor Osborn discussed the evolutionary phenomena which have 

 been named by him rectigradations or new structures and allometrons or 

 progressive changes of proportion. 



Professor Grabau, by means of lantern slides, exhibited convergent 

 evolution in certain phyla of fossil Gastropods, especially among Fusus- 

 like forms. 



The substance of Professor Broom 's remarks were as follows : I think 

 in the present condition of our knowledge that the introduction of a large 

 number of new terms is inadvisable. The three new terms introduced by 

 Gadow, representing three types of convergence, it is impossible accu- 

 rately to define, and Gadow himself admits that the distinctions are 

 vague. Doubtless the jumping foot of Macropns differs in structure from 

 that in Dipus, but the force which has produced the specialized foot in 

 the former is doubtless the same as has produced the jumping foot of 

 Dipus, the only difference being that Nature had somewhat different ma- 

 terial to work on. Gadow gives as an example of "parately" the wings 

 of pterosaurs and of birds. No doubt there is considerable difference both 

 in the appearance and in the intimate structure of those two types of 

 wings, but if we assume, as there is good reason to believe, that the ances- 



1 Science, N. S., Vol. XXXI, 11 Feb., 1910, pp. 201-210. 



