1911.] NATURAL SCIENCES OF PHILADELPHIA. 411 



Dahl (1884) found a very peculiar sense organ in the maxillae of 

 spiders. He called it an olfactory organ because he failed to find any 

 olfactory structure near the breathing apparatus and because its 

 location is not suitable for any other function. He performed no 

 experiments to determine its office. According to my experiments 

 it has probably not the slightest olfactory sense. He experimented 

 on various species with turpentine and clove oils, but was not able 

 to ascertain whether they have the power to distinguish differences 

 in various oils. Each oil repelled the specimens in a like manner. 



Dahl (1SS5) states that Bertkau does not agree with him in regard 

 to the histology of his so-called olfactory organ. 



The Peckhams (1887) experimented on various species with strong 

 smelling oils and perfumes. Three species, Epeira hortoum, Dolomedes 

 tenebrosus and Herpyllus ecclesiasticus did not respond to the test. 

 Sometimes the legs were rubbed between the palps and falces. Var- 

 ious other movements also were exhibited similar to those I have de- 

 scribed. Among spiders of the same species there was a great degree 

 of difference in the sensitiveness to various odors. 



McCook (1890) concludes from experiments and observations that 

 spiders have little sense of smell, although they are in some way 

 affected by certain odors. At first he entertained the opinion that the 

 sense of smell in spiders, like that of hearing, abides entirely in the 

 delicate hairs covering the creature. Later, judging from the experi- 

 ments of the Peckhams, he states that their experiments would indicate 

 that the olfactory organs are distributed more or less over the entire 

 surface of the body, especially at the tips of the feet and at the apex 

 of the abdomen. After the extirpation of the palps of two females, 

 there was no apparent loss of sensitiveness. 



Pritchett (1904) states that both kinds of odors, non-irritant and 

 irritant, repel both males and females in the same degree. Indi- 

 viduals with either palps, or first pair of legs, or tarsi of all legs removed, 

 responded normally when all the other appendages were intact. Also 

 they responded in the same way when the sense hairs were removed 

 from all the legs. 



(c) Sense of Hearing. 



Boys (1880) asserted that the garden spider responded readily to 

 the vibrations of tuning forks, but since this is an orb-weaver the web 

 certainly must have been irritated in some way to cause the so-called 

 auditory reactions. 



The Peckhams found that only web-makers responded to tuning 



