58 PROCEEDINGS OF THE ACADEMY OF [Jan., 



the outer seta of the type form is replaced in his variety by a spine. 

 There has been much confusion over this point. Herrick states 

 that the fifth foot has ''three spines." Miss Byrnes agrees in her 

 -description with Schmeil, for she finds "a coarse inner spine and two 

 setae." This is undoubtedly one of those details of structure which 

 may vary considerably, and I merely give the observations of the 

 investigators to show their opinions on this point. 



The receptaculum seminis (fig. 4, PL IV) is of a very characteristic 

 form. It consists of two portions. These are in the shape of long, 

 closely lying narrow ellipses. The upper portion has a slight inden- 

 tation in the middle of its anterior margin and the ends are slightly 

 upturned. The porus is situated in the middle of the short common 

 portion which connects the two divisions of this organ. The struc- 

 ture of the receptaculum seminis has never before been observed in 

 the American representatives of this variety. The egg-sacs contain 

 but a few dark ovae, 7-10, and are carried close to the abdomen in 

 life. 



I have found that 1.17 mm. is an average length for females of the 

 variety poppei. Schmeil gives .86 mm. and Herrick .8 mm. The 

 former states that "die Varietat ist etwas kleiner als die typische 

 Form." For the "typische Form" Schmeil gives for the female 

 "0.92-1 mm." The smallest mature female that I have measured 

 was 1.13 mm. long — longer than the typical European form. 

 Schmeil's observations on the size of this species does not seem to 

 hold good, then, for the American forms. In fact, the reverse is 

 true of specimens from this vicinity. Further study of the species 

 will undoubtedly show that type and variety are of a size. 



The variety poppei is practically colorless. Irregular chains 

 (fig. 5, PI. IV) of rose-colored globules are scattered occasionally 

 throughout both cephalothorax and abdomen, and the ovaries, when 

 distended, appear a deep shade of lavender. 



The most readily distinguished characters of this variety are the 

 short eight-jointed antennae (which show that it belongs either to the 

 type or variety) and the very characteristic armature of the dorsal 

 surfaces of the caudal stylets. 



The following table illustrates the main points of difference between 

 type and variety: 



