650 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXVII. 



Fig. 32. — Three posterior pair.s of leg; 



IX the male ARGULtS VER.SICOLOR. 



Reproductive organs. — These are similar in position and arrangement 

 to those of americanus, but the unpaired seminal vesicle in the male is 

 quite different in shape, being- nearly spherical, with an emarginate ante- 

 rior border. Another difference was the fact that, after removing the 



pigment from several males, no trace of 

 any accessor}" blind capsules could be 

 seen. The second legs of the male have 

 a large conical projection on their pos- 

 terior surface at the outer end of the 

 basal joint (fig. 32). There is a similar 

 much smaller one in a corresponding- 

 position on the third legs, and these 

 legs also have a rounded knob on the 

 anterior surface of the second joint at 

 the end next the body. 



But the chief interest, both iri this 

 species and americanus^ lies in the fact 

 that it was possible to ascertain in them 

 from actual observation the structure 

 and exact function of the semen recep- 

 tacle and peg upon the bases of the 

 third and fourth legs, respective!}'. 

 The peg consists of two parts, basal and terminal; the basal portion 

 is a blunt papilla whose walls are stiff' and covered with rough tuber- 

 cles (fig. 33). It does not appear to be hollow, but readily permits of 

 the withdrawal of the terminal 

 part inside itself. This termi- 

 nal portion is a slightly curved 

 conical tube, with walls as ff^xi- 

 ble as rubber and so thin as 

 to be perfectly transparent and 

 colorless. The tip of the tube 

 is somewhat enlarged and sur- 

 rounded by a row of minute 

 hairs. Inside both tube and 

 papilla can be seen a muscle 

 strand which extends from the 

 tip of the tube diagonally back- 

 ward to the posterior margin of 

 the leg. By means of this 

 muscle, together with the circular muscles in its own walls, the tube 

 can be withdrawn inside the papilla or protruded at pleasure. 



The semen receptacle is a cavity in the posterior part of the distal 

 end of the basal portion of the third legs; the opening into this cavity 

 is on the ventral surface, near the posterior margin. This opening is 



Fig. 33. — Basal joints of the two posterior legs 



OF male ABGULUS VErSICOLOR, SEEX FROM THE 

 ventral SURFACE. 



guarded by a strong sphincter muscle. 



