On the Structure of Peripatus capensis. 227 



short common tubes, which open all over the body by small outlets 

 in the epidermis ; these outlets have no regular structure, and are 

 difficult to see. The whole of the tracheal system, very conspicuous 

 in the fresh condition, becomes almost invisible when the animal 

 examined has been a short time in spirit and the air has been 

 thus removed from the tracheae. Hence the failure of Grube 

 to see them. The tracheae are distributed in meshworks to all 

 the viscera. The spiral filament is very imperfectly developed. 

 A row of larger oval spiracles exists along the middle line of the 

 under surface, the spiracles being placed opposite the interspaces 

 of the feet, but not quite regularly. Other large spiracles exist 

 on the inner sides of the bases of the feet. A large supply of 

 tracheae goes to the rectum and muscular pharynx. In many 

 points the structure of the tracheal system resembles that in Talus. 

 Peripatus is not hermaphrodite. Out of thirty specimens about 

 ten were males. No outward distinction of the sexes could be dis- 

 covered. The female organs consist of a small oblong ovary situate 

 behind the stomach, about one sixth of the length from the end of 

 the body ; from this lead a pair of oviducts, which, at their termi- 

 nations, become enlarged and perform a uterine function, appearing, 

 when filled with embryos, like a string of sausages. In nearly all 

 cases, even when the embryos were far advanced, two large masses 

 of spermatozoa were found in the ovary, and others attached to 

 the ovisacs externally. A long loop, formed by the oviducts on 

 each side, being quite loose in the body, becomes often thrown 

 into a knot through the constant protraction and retraction of the 

 body- wall. The knot is known to sailors as an overhand knot on a 

 bight. The knot sometimes becomes drawn very tight, and then 

 prevents the passage of the embryos above it. A case was met 

 with in which this had occurred. The upper parts of the oviducts 

 were mortified off at the knot, and remained attached only to the 

 ovary. The ducts were dilated into large single sacs, the usual 

 constrictions between the embryos having disappeared, and were 

 full of decomposed embryos and fatty tissue. The knot was met 

 with in many specimens — in some cases on both sides of the 

 body, in others on only one. The oviducts unite in a short 

 common tube to open at the simple vulva. The male organs con- 

 sist of a pair of large ovoid testes, surmounted by short tubular 

 prostates. The vasa deferentia are long and tortuous, forming, near 

 the testes, spiral coils in which the ducts are enlarged, and which 

 may be called vesiculae seminales. A muscular ejaculatory tube, or 

 penis, lies on one side of the body — sometimes on one, sometimes 

 on the other. One vas deferens passes across, at the end of the 

 body, under both nerve-cords to join the penis ; the other takes 

 a more direct course, not passing under the cords at all. In the 

 original condition both ducts probably passed one under each nerve- 

 cord, to join the centrally placed common terminal tube, homolo- 

 gous with that of the female organs. 



The spermatozoa are filamentary, as in insects and in Scolo- 

 pendra, but not in lulus. Their development is described. They 



