1911.] NATURAL SCIENCES OF PHILADELPHIA. 379 



function. In the specimens just moulted the sensory fibers were 

 never connected with the dilatations (di.) of the slits, merely because 

 they apparently had not had sufficient time for regeneration since the 

 casting of the old skin. But in specimens six or seven hours after 

 moulting a few of these connections were noticed, while in individuals 

 with thick cuticula many such connections were observed. Fig. 3 

 shows two of these sense cells as they actually occur in a section of 

 the trochanter of Th. tepidariorum six or seven hours after moulting. 

 Here the cuticula is broken as-usual, but one nerve fibre connects with 

 its dilatation, the other one has either been broken loose or has not 

 yet had time to join its dilatation since moulting. 



In good serial sections the nerve of the leg is very distinct and 

 branches from it can very readily be traced to the lyriform organs. 

 Within these branches the nerve fibres can quite easily be traced to 

 the sense cells. Usually the nerve is found near the axis of the leg, 

 but in some cases it lies closer to the hypodermis as shown in fig. 1. 

 Both the nerve and its branches are enclosed by a neurilemma (neu.) 

 whose walls show numerous nuclei (n. neu.). Internal to this neuri- 

 lemma the fibres are shown in cross section as the clear spaces with 

 here and there a cross section of a tolerably deep staining nucleus, 

 probably a neuroglia nucleus (neu. n.). These nuclei are about one- 

 third as large as those of the hypodermal cells; their nucleoli are 

 generally arranged around the periphery and their chromatin-network 

 as in the other kinds of nuclei is rather difficult to see. - The network 

 (neu. w.) of the nerve is probably the walls of these neuroglia cells. 



I was able to trace the innervation of a few of the single isolated 

 slits. Fig. 5, drawn from two consecutive sections of Th. tepidario- 

 rum six or seven hours after moulting, shows the sense cell with its 

 fibre connecting with the dilatation of the slit. This cell has a 

 similar position, shape, size and structure to one of those belonging to. 

 an organ. 



At certain places in the legs the muscles occupy almost all the space- 

 surrounded by the hypodermis, but generally near the lyriform organs 

 they are not so extensive. At almost any place one may choose at 

 least three or four such muscles (m. b.) as the one shown in the drawing 

 may be readily seen. The single walled sarcolemma (sar.) surrounds, 

 many muscle bundles, each one of which reveals either two or three 

 nuclei (m. nuc.) lying in the sarcoplasm. 



Each leg possesses a large artery (art.) which usually lies against 

 or near the nerve. It has a double wall which often shows nuclei. 

 Two large venous sinuses (v. sin.) are always present, one on the 



