STRUCTURE AND ECONOMY OF SPIDERS. 313 
of a solution on any other physiological principle that 
T am aware of. 
For some years past I have been engaged, occa- 
sionally, in conducting experiments having for their 
object the determination of a highly interesting ques- 
tion in physiology—namely, what are the true nature 
and functions of the remarkable organs connected 
with the digital or terminal joint of the palpi of male 
spiders? The opinion advanced by M. Treviranus, 
and adopted by M. Savigny, that those parts are 
instruments employed for the purpose of excitation 
merely, preparatory to the actual union of the sexes 
by means of appropriate organs situated near the 
anterior extremity of the inferior region of the abdo- 
men, is in direct opposition to the views of Dr. Lister 
and the earlier systematic writers on arachnology, 
who regarded them as strictly sexual ; and the results 
of my own researches, which I shall proceed to detail, 
clearly demonstrate the accuracy of the conclusions 
arrived at by our celebrated countryman. 
In the spring of 1831 I procured young female 
spiders of the following species :—Zpeira diadema, 
Epeira apoclisa, Epeira calophylla, Epeira cucurbitina, 
Theridion nervosum, Theridion denticulatum, Agelena 
labyrinthica, &c., and having placed them in glass 
jars, I fed them with insects till they had completed 
their moulting and arrived at maturity, which is easily 
ascertained, in most instances, by the perfect deve- 
lopment of the sexual organs. I then introduced to 
