390 



PROCEEDINGS OF THE ACADEMY OF ' [May, 



ever, remaining the stouter. Probably as a result merely of their being 

 less worn, the points are usually longer and sharper than on more ante- 

 rior setae. At the point indicated the dorsal bundles become abruptly 

 reduced to a single seta of very characteristic form (fig. 15). These are 

 very large and stout, especially in the outer limb, which joins the inner 

 one in an abrupt elbow marked by a prominent enlargement. The tip 

 remains bifid, but is formed almost entirely by the stout, strongly 

 hooked proximal division, which bears the small, slender distal division 

 as an accessory process on its convexity. In intact individuals such 

 large setae continue nearly or quite to the caudal extremity, but in 

 those which are regenerating the dorsal as well as the ventral bundles 

 contain unmodified setae, which are consequently here probably pro- 

 visional. 



The ventral setae of X, which lie just anterior to the orifice of the 

 spermathecae, are much modified as copulatory set^e (fig. 17). Usually 

 each fasciculus is reduced to one functional and one developing seta. 

 The former is about one-third longer than the ordinary sets, with a 

 very long slender outer limb cm^ved in the same direction as the inner 

 limb and deeply cleft into two delicate, very slightly diverging prongs, 

 which are, however, united by a thin curved plate to form a groove. 

 The setae sacs are also enlarged and their outer thirds form eversible 

 sheaths or pockets for the setae, and their closed ends receive the 

 secretion of two or three small groups of gland cells. 



The preservation of the specimens is unsatisfactory, so that histolog- 

 ical details are avoided in the following description of the internal 

 anatomy. The digestive tract consists of a short eversible buccal 

 chamber in I and II, a pharynx with a conspicuous spheroidal and 

 glandular dorsal diverticulum in III, a short oesophagus extending 

 through IV and V, and an intestine with its chlorogogue covering from 

 VI onward. The septa ~, ^, ^^ and ^^^ are thickened, muscular, and 

 carried back to the alimentary canal in the form of funnels. The last 

 is especially muscular. 



While a true integumental plexus appears to be absent, the vascular 

 system is conspicuous from the great development of the anterior 

 lateral vessels, which are very long and arranged in a series of loops 

 and folds beside the alimentary canal as far back as the genital somites 

 (X and XI), those in the latter especially being enlarged, somewhat 

 moniliform and extending into the sperm sac and ovisacs respectively. 

 The lateral vessels of VIII are also of large size, but whether they form 

 contractile hearts is uncertain. A highly developed gridiron plexus 

 of blood-vessels exists in the walls of the intestine, especially in the 



