MOULTING HABITS OF SPIDERS. 



IIB 



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, o 

 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 

 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 

 mode of immediate insertion of the 

 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 

 these animals. For tlie 

 these are so grouped as 

 folium or rude figure of 

 a leaf with various irregularities, as 

 scallops and dentations, upon the 

 edge. The thickenings first de- 

 scribed are always of a yellow col- 

 or, more or less 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 



FiCi. 74. 



(After Wagner. 



Rejected tegument of spider's 

 abdomen, ventral part, showing points for muscular 

 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. 



Fig. 75. Fig. 76. 



Points of Insertion of Dorso-ventral Muscles. 

 Fig. 75. Exterior tuberculous sculpture, with thick- 

 ening. Fig. 76. Interior cells, without thickening, 

 (After Wagner.) 



