346 Mr. H. N. Moseley on the Structure [May 21, 



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%f the bases of the feet. A 

 large supply of tracheae goes to the rectum and muscular pharnyx. In 

 many points the structure of the tracheal system resembles that in 

 lulus. 



Peripatus is not hermaphrodite. Out of thirty specimens about ten 

 were males. No outward distinction of the sexes could be discovered. 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 terminations, become enlarged and per- 

 form 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 knob 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 (as in that figured) on only one. The oviducts unite 

 in a short common tube to open at the simple vulva. The male organs 

 consist 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, homologous with that of the female organs. 



The spermatozoa are filamentary, as in insects and in Scolopendra, but 

 not in lulus. Their development is described. They are very long, and 

 their tails have a spiral movement as well as an undulatory one. They 

 twist into all sorts of loops. 



The muscular tissue of Peripatus is unstriated. 



The development of Peripatus was only partially followed. As a rule, 



