332 M. F. Dalil on the Auditory and 



for anatomical iuvestigation. The cup is very fine and large 

 in Pachygnathttj as shown in figs. 1 and 2 *. 



The hairs usually do not stand exactly in the middle of the 

 dorsal surface, no matter whether one or two series are jjresent, 

 because along the middle, immediately beneath the matrix, 

 there runs a Ijlnod-sinus (Hg. 1, hi), in wiiich the blood flows 

 towards the body. This is recognized in the preparation by 

 its finely granular nature. Beneath the blood-vessel lies the 

 main nervous cord of the leg (h), which may be pretty easily 

 detected in the dense mass of transversely-striated muscles by 

 its long irregularly arranged nuclei. From this main cord 

 branches are given off to the individual hairs. If we wish 

 to obtain a distinct picture of the course of the nerves, we must 

 not make an exactly sagittal section, but the section must form 

 an acute angle with the sagittal plane. 



The delicate nervous branches which run to the cups are 

 generally surrounded by pigment-grains, and thus their course 

 is rendered particularly recognizable. The pigment accumu- 

 lates especially beneath the chitinous envelope, and at the spot 

 where the nerve passes into the main nervous cord. Before 

 this passage the nerve is surrounded by three or four lighter 

 ovals, as is shown in the figure, and these also are bounded 

 by pigment-grains. The cup, the side walls of which are 

 formed by the chitinous integument, is various in form, very 

 shallow in the Chernetidaj, for example, and in the spiders 

 usually more or less globular. In Pachygnatlia Listerij 

 Sund., it is furnished with granular longitudinal costaa. At 

 the bottom of this cup there is a second smaller cup, which 

 projects freely from the bottom of the large one. This is 

 filled with a finely granular substance, upon the surface of 

 which the hair is inserted, while the nerve enters its lower 

 part. The auditory hairs are probably never quite simple at 

 the apex, certainly often very shortly and indistinctly plumose, 

 but sometimes, as in the Lycos idee, and especially in ISegestria^ 

 almost pectinate. When several are present a gradual in- 

 crease outwards is always shown. Earely there is a smaller 

 and, as it were, accessory hair between tiiose growing regu- 

 larly. When such a hair is present it is always very closely 

 c^pproximated to the neighbouring ones. When two rows 

 are present side by side, the shorter one usually increases 

 more rapidly in length, so that the last hairs do not differ too 

 much in length ; and this circumstance sometimes renders it 

 possible in doubtful cases to recognize whether we have before 



* In staining my preparations I employed Grenadiers liaematoxylin- 

 solution, whicli here, as in insects, gives the lest nuclear staining. 



