64 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 97 



corresponding with a pair of transient rudiments of preantennal 

 appendages mentioned by Kennel in Peripatus edwardsi. 



The coelomic sacs of the body region conform with the series of 

 postoral somites. The sacs of the jaw somite soon disappear. Those 

 of the following somites attain a high state of development during the 

 early embryonic period, leaving thus no doubt that the Onychophora 

 are descended from typically metameric ancestors. The coelomic 

 cavities become connected with the exterior by ventral diverticula 

 from the mesodermal walls of the sacs (fig. 32 C, c) that unite with 

 ectodermal invaginations {d), and thus form ducts opening on the 

 mesal aspects of the bases of the legs (D). These outlet ducts of 

 the coelomic sacs (coelomoducts) probably served primarily in the 

 early history of the Onychophora for the discharge of excretory 

 products and the gametes (fig. 34 A) ; but the coelomic sacs of the 

 somites anterior to the somite of the definitive genital outlets become 

 differentiated into dorsal gonadial and ventral nephridial compart- 

 ments (B, C, a, b). The gonadial compartments eventually disappear 

 except in a few posterior segments where they unite to form the 

 gonads ; the nephridial compartments are reduced to the form of 

 delicate vesicles at the inner ends of the coelomoducts (D, b), and 

 thus persist as end-sacs of the definitive nephridia. In the somite of 

 the genital outlet the entire coelomic sacs (figs. 32 E, 34 E, a, b) with 

 their coelomoducts (d) are converted into the lateral genital ducts. 

 The sacs of the second postoral somite become the salivary glands 

 that open into the preoral mouth cavity. Derivation products of the 

 coelomic walls include the entire muscular system, the dorsal pulsating 

 blood vessel (fig. 2g, DV), and a muscular dorsal diaphragm (DDph) 

 beneath the blood vessel. 



THE SOMATIC MUSCULATURE 



The body musculature of the Onychophora is in general similar to 

 that of the annelids in so far as it consists mostly of flat sheets or 

 bands of circular, oblique, and longitudinal fibers closely applied to 

 the integument throughout the length of the animal (fig. 29), but it 

 includes a series of lateral dorsoventral fibers {dvni) along each side 

 of the body cavity, which have no representatives in annelid muscu- 

 lature. These lateral muscles divide the body cavity into a median 

 compartment {niBC) containing the alimentary canal (AlCnl) and 

 the slime glands (SlmGld) , and lateral compartments (IBC) enclos- 

 ing the salivary glands (SIC Id), the nephridia (Nph), and the nerve 

 cords (NC). The muscle fibers are all very slender, and for the 



