The Sense of Sight lu Spiders 



287 



are directed a little more outward and in Phidippus a little more 

 downward also, than the same eyes in the adult. In Heteropoda, 

 on the contrary, the anterior middle eyes of the spiderling are 

 directed much more frontward than in the adult. 



The anterior side eyes in Phidippus and Lycosa are directed 

 much more toward the side than in the adult, in Heteropoda much 

 more toward the front. The angles of projection on the two 



TABLE IV 



SHOWING THE ANGLES THAT THE AXES OF THE EYES FORM WITH THE THREE PLANES OF THE BODY IN 



VERY YOUNG SPIDERLINGS 



a Projection on the horizontal or foundation plane. Compa'-e Figs. 4, 5 '^'z.r/ 7 



AME 



ASE 



PME 



PSE 



Phidippus tripunctatus. 



Lycosa nidicola 



Heteropoda venatoria.. 



30 

 30 



60 



c Projection on the plane of symmetry. Compare Figs. 4y 5 ^"'^ 7 



AME 



ASE 



PME 



PSE 



Phidippus tripunctatus. 



Lycosa nidicola 



Heteropoda venatoria. . 



-5 



+ 30 

 + 87 



Other planes could not be ascertained for these eyes. It is impos- 

 sible to study the posterior middle eyes in the young spiderlings 

 of Phidippus at all, on account of their extreme minuteness. In 

 Lycosa the projections of the axes of these eyes on the horizontal 

 plane is approximately the same as in the adult but their pro- 

 jection on the plane of symmetry shows that they are directed 

 upward at an angle about three times as great as in the adult. 



