IOWA ACADEMY OF SCIENCES. 47 



There is information at hand which points to an excess 

 of loops in the families of both Mr. and Mrs. A. But rely- 

 ing simply on the records contained in the prints from the 

 persons here mentioned, there seems to be good reason to 

 conclude that there is a decided tendency to hereditary 

 transmission of the type or general class of patterns. This 

 is further supported by resemblances in the lesser char- 

 acteristics of the patterns studied, such as their general 

 regularity, the fineness of lines, slope and size of the loops, 

 the sub-class of whorls where they occur, and the general 

 symmetry of the prints. When these are considered it 

 appears fairly certain that a decided family likeness in 

 finger patterns is transmitted to the children and the 

 grandchildren. 



FACTORS OF EXTINCTION. 



BY HEEBERT OSBORN. 



While w^e have come to recognize clearly the fact of 

 extinction of animal types and their replacement by other 

 forms of life there appears to have been less attention to 

 the special factors concerned in such extinction, or, to put 

 it differently we have been devoting our attention espe- 

 cially to the factors concerned in the production of new 

 types, the variation and evolution of animals, rather than 

 the factors of extinction. It is true that these may bear a 

 close relationship and present mutual dependencies and pos- 

 sibly we might take them as necessary corollaries or consider 

 factors of extinction as merely negative factors of evolu- 

 tion, but it seems to me worth while to attempt a distinct 

 formulation of those factors especially concerned in the 

 elimination of life forms even if for no other purpose than 

 to emphasize those factors of progressive evolution against 

 which they contrast. 



In the first place there is a certain kind of elimiuation 

 which can hardly be called extinction in the proper sense. 

 I refer to the progressive evolution by which a particular 



