AMERICAN ZOOLOGISTS AND EVOLUTION. 181 



changes in the direction of the fibres of the wood as the longer length 

 of the trying-plane could not conveniently deal with. Hitherto, we 

 have regarded the plane as arranged with a " guide principle " which 

 shall always repeat a straight, level surface. The guide may, how- 

 ever, be the counterpart of any required surface. The plane made of 

 iron, now in my hand, has an elastic steel sole, which, by means of 

 adjusting screws, enables a workman readily to convert a straight- 

 faced sole into one either concave or convex. This is an American 

 production {see Fig. 10). 



Fig. 10. 



There is also in this and other planes a mode of fixing the iron 

 which deserves more general adoption than it receives, viz., by a cam- 

 action. It will often be noticed that, where the holding-wedge binds 

 on the box of the plane in our ordinary planes, the wood has split. 

 This arises from a commendable but, in this case, too strict a care 

 for a good fit; hence the wedge is made tight where it should be 

 slack. 







WHAT AMERICAN ZOOLOGISTS HAVE DONE FOR 



EVOLUTION. 1 



By Professor EDWAED S. MOESE, 



II. 



IN the "Memoirs of the American Academy of Sciences" may be 

 found a profound mathematical essay " On the Uses and Origin of 

 the Arrangement of Leaves and Plants," 2 by the lamented Chauncey 

 Wright. After discussing the laws of phyllotaxy, and showing that 

 the botanist is wrong in supposing this a law at the outset, Mr. 

 Wright states " one of the utilities, so to speak, in the apparently 



1 An address delivered at the meeting of the American Association for the Advance- 

 ment of Science. Read at Buffalo, New York, August, 1876, by Edward S. Morse, Vice- 

 President of Biological Section. 



* " Memoirs of the American Academy," vol. ix., p. 379. 



