1911.] NATURAL SCIENCES OF PHILADELPHIA. 38& 



are all long; XII 9-2, latter two are long ones; XIII 17-12; XIV 

 8-4; XV and XVI 4-2 each; XVII 6-2, young as adult with an asso- 

 ciated slit; XVIII 6-2. By referring to the table (p. 389) we see 

 that while the adult female has 60 compound organs, its young just 

 hatched has only 38. By counting all the slits enumerated above the 

 adidt has a few more than twice as many as the young, then 

 by including the isolated slits in both we see as far as number is con- 

 cerned, that when the young are hatched the lyriform organs are 

 hardly one-half developed. Thus after hatching the slits in the organs 

 more than double themselves; organ No. 1 on the palps, the diffused 

 organ No. 3 on the legs and the majority of the isolated slits make 

 their appearance. 



(b) Other Species. 



In order to ascertain most of the variations found in the other 

 species, reference is made to the tables on pp. 386-393. At the top of this 

 table the families are arranged as Simon recognizes them. Just 

 below the family names are entered the subfamilies, the generic and 

 specific names. The following abbreviations are employed : H, hun- 

 ters; S, snarers; T, tube-dwellers; the numbers 1 to 7 for the joints 

 of the legs correspond to coxa, trochanter, femur, patella, tibia, meta- 

 tarsus, and tarsus. Spinn., spinnerets; Chel., chelicera; Max., maxilla; 

 Lab., labium; Stern., sternum; Ped., pedicle; Ceph. S., cephalo- 

 thoracic shield and Near Epigy., includes all the organs on the ven- 

 tral side of the abdomen, usually occuring near the epigynum; C. (). 

 and S. O., compound and simple organs, and S. S., single slits. 

 Where only one segment is present in the spinnerets I have con- 

 sidered it the first one, although it may correspond to the second 

 or third in other cases. All the specimens were adults. The young 

 of Th. tepidariorum is entered only for comparison, but has not 

 been considered in the range or in the comparison of the adults.. 

 The total includes all the organs and slits which could be found 

 on all the legs, palp, spinnerets, cheliceron, and maxilla on one side 

 of each specimen. Hence the total contains slightly more than one- 

 half the number for each individual. For the number of organs 

 the amount of error is probably not greater than two per cent. r 

 while for the single slits not more than ten per cent. The latter 

 possibility of error is largely due to the three following reasons: (1) 

 the slits when placed in profile are never discernible; (2) on account of 

 the transparency; (3) the caustic potash treatment often causes- 

 artificial slits and no doubt often destroys some of those present. 



