the tapirãs lateral {742} toe is a precisely identical function of the form F ÿ£¢( e ÿ£¢ x ÿ£¢,ã₤ y ÿ£¢ 1 ) =ã₤0, where x ÿ£¢ 1 ã₤, y ÿ£¢ 1 are oblique co-ordinate axes inclined to one another at an angle of 50ô¯.
Dû¥rer was acquainted with these oblique co-ordinates also, and I have copied two illustrative figures from his book15.
In Fig. 367 I have sketched the common Copepod Oithona nana, {743} and have inscribed it in a rectangular net, with abscissae three-fifths the
Fig. 367. Oithona nana. Fig. 368. Sapphirina.
length of the ordinates. Side by side (Fig. 368) is drawn a very different Copepod, of the genus Sapphirina; and about it is drawn a network such that each co-ordinate passes (as nearly as possible) through points corôÙreôÙsponôÙding to those of the former figure. It will be seen that two differences are apparent. (1) The values of y in Fig. 368 are large in the upper part of the