32 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 95 



responding gonoduct. Both the gonad and the duct are ensheathed in 

 a muscular coat. The tubular form of the gonad may be retained in 

 the adult, but generally the primary tube becomes branched, produc- 

 ing either a pair of lengthwise tubes, or more commonly a number of 

 lateral diverticula. In some cases the two gonads of opposite sides 

 are united in a single tube or elongate sac, which is either simple or 

 branched. In the Scorpionida mesal branches of the primary gonadial 

 tubes are generally united with each other forming a series of loops, 

 which may join with those from the opposite side, particularly in the 

 female, to produce a composite gonad having the form of a wide- 

 meshed net (see Pavlovsky, 1924, 1924a). The gonad of the net type 

 in the scorpions resembles the reticulate gonad of XipJwsitra (fig. 8 B) 

 except that the latter has a much finer mesh, but the union of the 

 gonadial branches appears to be independently evolved in the Scor- 

 pionida, and is thus no evidence of close relationship between the 

 scorpions and the xiphosurids. In the arachnid ovaries the eggs are 

 developed singly in numerous small follicular diverticula of the ovarian 

 tubes, a feature which the arachnids have in common with Xiphosurida 

 and Onychophora. The embryos of the viviparous scorpions develop 

 either in swellings of the ovarian tubes between the egg follicles or 

 in the follicles themselves. 



The gonoducts, regardless of the form of the gonads, are always 

 a single pair of tubes extending usually forward from the ovaries or 

 testes. In both sexes of Scorpionida, in the males of Solpugida and 

 Phalangida, and in the females of Chelonethida, the gonoducts open 

 separately into the genital chamber (fig. 4 G), but in most other cases 

 they unite in a common duct (H) or an inner sac (I) that discharges 

 into the external genital chamber. Since neither the common duct nor 

 the inner chamber is ever found to have a chitinous cuticular lining, 

 the two appear to be structures of mesodermal origin probably formed 

 by the union of the distal parts of the primary mesodermal ducts. 

 The common duct in this case is not strictly equivalent to the usual 

 ectodermal ductus ejaculatorius or the oviductus communis, and is 

 hence here termed a ductus conjunctus (fig. 4 H, J, Den). The inner 

 sac (I, Si), which is evidently an enlargement of the ductus con- 

 junctus, is commonly called the " uterus internus " in arachnid 

 anatomy, the name being applied alike in both the female and the 

 male, but since the organ is not functionally a uterus even in the 

 female, it is here termed the saccus internus (Si). The walls of the 

 inner sac have a strong sheath of muscle fibers, and both the sac and 

 the ducts may be provided with glandular and other kinds of diver- 

 ticula, including the complex " paraxial organs "of male scorpions 

 described by Pavlowsky (1924). 



