36G Alexander Petrunkevitch, 



leg- of the tarantula, force it at tlie end of fifteen seconds or more, 

 to lift the leg*. Grasshoppers, crickets and certain beetles having' 

 a strong: odor, when placed. at the same distance, produced no effect 

 whatever and the question whether Bugesiella possesses a real, if 

 poor sense of smell or reacts to the direct Irritation of the skin, 

 caused by the vapors of the reag-ents, remains unanswered. So 

 niuch is clear, however, that Dugesiella neither recognizes nor per- 

 ceives the presence of live insects or spiders from their odor, There 

 remain, therefore, two senses by means of which Dugesiellas may 

 be supposed to recognize other individuals of their own species and 

 their prey, the sense of sight and the sense of touch. Since they 

 possess four pairs of eyes, it was necessary that their sense of sight 

 should be thoroug-hly investigated before a definite conclusion could 

 be reached, I have used the same methods as in my previous study of 

 the sense of sig-ht in spiders, but have also made some experiments 

 and observations with the object of Controlling the results. 



The eyegroup of DugesieUa, represented in Textfig. B consists 

 of three types of eyes, two of which are new to seien ce. 



The following measurements are taken from the male described 

 above. 



Anterior middle eyes have a circular lens: diameter 0,2622 not 

 counting the iris. 



Anterior side eyes have a lens shaped like an imperfect elipse ; 

 long axis 0,4140; short axis 0,2622. 



Posterior middle eyes are more or less oval in shape; long axis 

 0,2622; short axis 0,1794. 



Posterior side eyes have almost the same shape as the anterior 

 side eyes but are a little smaller; long axis 0,3450; short axis 

 0,1794. 



The anterior middle eyes have the same structure as the 

 corresponding eyes in all other spiders. They form clear and sharp 

 Images without aberration, but the diameter of the rods in so great 

 that the Image of one Square centimeter at a distance of 20 centi- 

 meters from the lens falls only on a Single rod. The remaining six 

 eyes are with inverted retina but differ from the corresponding eyes 

 in true spiders in that they have no vitreous body, the cells of 

 the retina lying directly und er the lens. The diameter 

 of the rods is a trifle greater than in the anterior middle eyes, the 

 largest rods being found in the posterior middle eyes, where the 

 entire retina is composed of comparatively few cells. In these eyes 



