Fast eBooks

I have therefore
prepared some diagrams in which each of the individual birds measured is
represented by a spot, placed at a proportionate distance, right and
left, from the median line accordingly as it varies in excess or defect
of the mean length as regards the particular part compared. As the
object in this set of diagrams is to show the number of individuals
which vary considerably in proportion to those which vary little or not
at all, the scale has been enlarged in order to allow room for placing
the spots without overlapping each other.
In the diagram opposite twenty males of Icterus Baltimore are
registered, so as to exhibit to the eye the proportionate number of
specimens which vary, to a greater or less amount, in the length of the
tail, wing, tarsus, middle toe, hind toe, and bill. It will be noticed
that there is usually no very great accumulation of dots about the
median line which shows the average dimensions, but that a considerable
number are spread at varying distances on each side of it.
In the next diagram (Fig.


Pages:
103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127