^ The American Naturalist. [Jinu-irv, 



have had upon it is lost, unless the effect is preserved in the 

 seed ; and it does not matter how many generations have lived 

 under the given uniform environment, for the plant starts all 

 over again, de novo, each year. Therefore, the environment 

 must affect the annual plant in some one generation or not at 

 all. It seems to me to be mere sophistry to say that in plants 

 which start anew from seeds each year, the effect of environ- 

 ment is not felt until after a lapse of several generations, for if 

 that were so the plant would simply take up life at the same 

 place every year. This philosophy is equivalent to saying 

 that characters which are acquired in any one generation are 

 not hereditary until they have been transmitted at least once ! 

 My contention then, is this : plants may start equal, either 

 from seeds or asexual parts, but may end unequal ; these in- 

 equalities or unlikenesses are largely the direct result of the 

 conditions in which the plants grow; these unlikenesses may 

 be transmitted either by seeds or buds. Or, to take a shorter 

 phrase, congenital variations in plants may have received 

 their initial impulse either in the preceding generation or in 

 the sexual compact from which the plants sprung. 

 Cornell University, Ithaca, K Y. 



A COMPARATIVE STUDY OF THE POINT OF ACUTE 



VISION IN THE VERTEBRATES. 1 



By J. R. Slonaker, 



In this preliminary sketch of a comparative study of the 

 eyes of vertebrates, with special reference to the fovea centralis 

 or point of acute vision, I shall first give the processes and 

 methods of preparation which I have used and results ob- 

 tained, and, second, the position of the area centralis as indi- 

 cated by the retinal arteries. The microscopic descriptions 

 and the relation of the position and shape of the eye and ar- 

 rangement of the retinal elements to the habits of the animal 

 will follow in a later paper. 



1 1 wish to thank Dr. C. F. Hodge for valuable assistance and for his method 

 of injecting the eye-ball, thus preserving it for complete sections. I am also very 

 much indebted to Clark University for valuable aid and for apparatus and mate- 



