1911.] NATURAL SCIENCES OF PHILADELPHIA. 395 



one, but in most cases two transverse single slits like c and d. Be- 

 sides these in many species there are several other smaller transverse 

 slits. These usually lie near the larger ones but not so near the distal 

 end. (10) Fig. 29 shows three slits and three hairs found on 

 the first joint of the spinnerets of Evagrus. Organs on the spinnerets 

 occur in only five species. In Hytiotes there is a small transverse 

 compound organ at the base of the spinnerets; at the same place in 

 the male of Troglohyphantes and Epeira this organ is transverse and 

 simple (fig. 19). On the ventral extreme distal end of the first 

 joint of Mimetus there is a transverse organ of nine slits; at the 

 same location on the foremost spinneret of Tama there is a large 

 transverse organ with eleven slits (fig. 33). (11) For the chelicera, 

 fig. 28 shows two of the four simple organs found in Dictyna. Here 

 the border is entirely absent. In Hyptiotes (fig. 20) the border sur- 

 rounds all the slits of each organ. Fig. 11 shows the very large 

 organ in Moggridgea. (12) Fig. 21 represents two of the thirteen 

 slits on the labium of Ariadna. (13) Whenever the number of slits 

 on the sternum is approximately 24, they are arranged in groups 

 of threes. In such cases the proximal end of each coxa faces one 

 of these eight groups. Whenever the number is much smaller than 

 24, they are not arranged in groups, but are scattered irregularly. 

 Whenever the number is much more than 24, then they are grouped 

 as in Th. tepidariorum. (14) Fig. 36 shows two of the twenty very 

 small slits on the pedicle of Moggridgea. (15) When the minute slits 

 can be detected on the cephalothoracic shield they occur usually at 

 either side or directly in front of the pedicle. Fig. 46 shows three 

 taken from Ariadna. (16) Near the epigynum we have the follow- 

 ing: Fig. 22 shows two of the twelve scattered slits in the. female of 

 Pholcus. These twelve are found on both sides of the epigynum a 

 little above the ones marked j in Th. tepidariorum. Fig. 54 shows a 

 group of these in Moggridgea. They are drawn much too close to- 

 gether. Fig. 43 represents the two diffused organs in front of the 

 epigynum of Calculus, while fig. 47 shows one of the two organs in 

 front of the epigynum of Dysdera. In only a few cases have the two. 

 pairs of large slits been found which lie between the epigynum and 

 spinnerets as shown in Th. tepidariorum. 



(c) Individual and Sexual Variations. 



For a study of the individual variation, I have used the fourth pair 

 of legs of ten males and ten females of Th. tepidariorum, thus making- 

 forty legs in all. Organ No. 1 in the females occurs nine times to 



