MOULTING HABITS OP SPIDERS. 



113 



these there is a large number of points of immediate insertion of the 

 muscles upon the cuticle without thickening of the chitine at that point. 



Like conformations are observed upon the dorsal face of the abdomen. 

 These are near the local thickenings of the chitine at the points of inser- 

 tion of the dorso-ventral muscles, 

 and in the interval comprised be- 

 tween the lines of the local thick- 

 enings upon the dorsal face and the 

 lateral line of thickenings. (Fig. 

 74, Nos. 17 and 39.) 



An examination of rejected teg- 

 uments shows the existence of two 

 forms of points of insertion, which 

 differ in structure and size. One 

 presents a thickening, more or less s 

 considerable, of a sculpture tuber- 

 culous upon the exterior (Fig. 75), 

 and having a row of cells and walls 

 more or less thick upon the inte- 

 rior. (Fig. 76.) Each of these cells 

 serves for a point of immediate in- 

 sertion upon a fasciculus of muscles, 

 so that the number of cells indicates 

 the number of fasciculi. The other 



FIG. 74. (After Wagner.) Rejected tegument of spider's 

 mode Of immediate insertion Of the abdomen, ventral part, showing points for muscular 



muscles shows no thickenings of the 



chitine ; but one observes at these 



points upon the tegument certain 



linear thickenings, hardly distinct, which indicate the limits of the point 



of insertion of the muscles and of each of the fibres taking part. 



One can hardly fail to note that the arrangement of these points of 



attachment indicates in a general way, and indeed with tolerable accuracy, 



the outlines of the markings which 

 distinguish these animals. For the 

 most part these are so grouped as 

 to form a folium or rude figure of 

 a leaf with various irregularities, as 

 Fl(i - 75 - FlG - 76 - scallops and dentations, upon the 



PO.NTS OF INSEBTION OF DOBSO-VENTBAL MUSCLES. ^ The thickenings first de- 



Flu. 75. Exterior tuberculous sculpture, with thick- f 



ening. Flo. 76. Interior cells, without thickening. SCribed are always 01 a yellOW COi- 



(After wagner.) orj mme Qr legg intense; a color 



which is the dominant one in nearly all families of spiders showing decided 

 hues. In the second form of attachment the cuticle is colorless and trans- 

 parent. In both cases the skin above the points of insertion is without 



' 



attachment ; o, genital orifice ; pr, pores ; 1-16, sixteen 

 pairs of points of insertion of two median series of 

 muscles ; 17-39, twenty-three pairs of points of inser- 

 tion for two lateral series ; pou, gills. 



