384 PROCEEDINGS OF THE ACADEMY OF [May, 



contains about one-half the total sternal slits, is midway between the 

 median line of the sternal plate and the outer edge of the sternum 

 (fig. 13). In the group of five slits (figs. I3i, 42) no two are of the 

 same size or shape. The first and third largest ones do not have any 

 distinct dilatation, while the other three do. The second largest slit 

 besides having its border also has a much darker colored circular disc 

 which lies across the border at its middle. 



On the ventral surface of the abdomen, we find a large isolated slit 

 on either side of the epigynum near the lower end of the lung-book 

 (figs. 13/, 44a). Lower down at the same distance from the edge of 

 the abdomen midway between the epigynum and spinnerets, there is 

 another pair of large isolated slits. Just in front of the spiracle 

 there is another pair slightly smaller than the two preceding pairs 

 (fig. 13). On the left spinneret of the first pair there are three small 

 isolated slits (figs. 13k, 446). 



At the right posterior side of the cephalothoracic shield just above 

 where the right fourth leg is attached there are two minute indistinct 

 isolated slits (fig. 14). 



The lyriform organs found in the seventeen day (just hatched) 

 spiderling of Th. tepidariorum have the same disposition as the cor- 

 responding ones in the adults. But there are none on the first joint 

 of the palps, the spinnerets, maxillae, labium, sternum, cephalothoracic 

 shield and near the epigynum. In other places the isolated slits are 

 very scarce. As compared with the organs of the adult female, those 

 of the spiderling have almost proportionately the same size, but since 

 the number of slits in the latter is about one-half that of the former, 

 the slits are proportionately larger. In order to compare the number 

 of slits in each organ of the spiderling with that of the adult female, 

 I shall indicate the number of each organ with a Roman letter and the 

 number of slits in it with an Arabic figure. In each case the number 

 of adult slits appears first and of the juvenile second. 



Palps.— I 2-0; II 7-5; III 0-0; IV 7-5; V and VI 7-2 each; 

 VII 0-0; VIII 10-4, but the latter does not have the same shape as 

 former; IX 7-4; all others are absent as in the adult, but the large 

 slits on both palps and legs marked a, b, c, and d are present as in the 

 female. 



Legs. — I 3-2; II 15-5, but the latter are all long and of equal length; 

 III 7-0; JY 14-5, latter are all long and of equal length; V and VI 

 11-4 each, latter four all long and of equal length; VII 17-S; VIII 

 21-10; IX 6-3, in latter no isolated slits ever accompany organ as in 

 the former; X 6-2; XI 11-6, in latter slits are about same length and 



