18 



GARDNER CHENEY BASSET 



Sixth Average — 

 Seventh Average . 



Sixth Average — 

 Seventh Average . 



Sixth Average — 

 Seventh Average . 



Sixth Average — 

 Seventh Average . 



Sixth Average 

 Seventh Average 



TABLE lid 

 The Maze 

 Anatomical Data of Sixth and Seventh Generation Inbred Rats 



Body 

 Length 

 in mm. 



Sixth Average 200.71 



Seventh Average 184 . 71 



Water 



in Cord 



per 



cent 



Sixth Average 71 . 73 



Seventh Average 71 . 70 



Body 



Weight 

 in grms. 

 195.04 

 152.47 



Brain 

 Weight 

 in grms. 

 1 , 75234 

 1.63286 



Per cent 



Brain Weight 



in Relation to 



Body Length 



.87418 



.88219 



Cord 



Weight 



in grms. 



.53881 



.50794 



Per cent 



Brain Weight 



in Relation to 



Body Weight 



.91653 



1.07851 



Water 



in Brain 



per cent 



78.49 



78.51 



killed 

 Days 



196 

 207 



In Plate IV is shown the curve of learning (below) and of 

 relearning (above) of the 6th generation of inbred rats compared 

 with those of the 7th. These curves are constructed from figures 

 given in Table II. The curve of the 6th generation rats is indi- 

 cated by the broken line, that of the 7th generation by the soHd 

 line. The ordinates show the average daily time in seconds for 

 each group, and the abscissae the number of the day in which 

 such time was made. From the twenty-second day the curve 

 of learning of the 6th generation lies below the six-second mark, 

 and from the eighty-third day is fiat at 5.158 seconds, signi- 

 fying that on that day the last of this group had perfected the 

 habit. The 7th generation learning curve is very irregular 



