14 THE ANATOMY AND DEVELOPMENT OF PERIPATUS NOVAE-BRITANXIAE. 



of the intestine, and retains its dorsal position until its descending portion reaches 

 approximately the point where the intestine passes into the rectum, when it becomes 

 concealed below the left uterus for the rest of its course to the vagina. The ascending 

 left uterus (Figs. 3, 4) has a straight course forwards along the ventral wall of the 

 body-cavity to the right of the intestine until it bends over into the descending portion 

 of the same uterus, the loops of which were deeply imbedded in the wall of the gut. 

 On reaching the point where the intestine passes into the rectum the descending left 

 uterus passes below the alimentary canal from the right side to the left and finally, as 

 we have seen, passes over the rectum with an arcuate bend until it reaches the posterior 

 end of the body, when it passes below the left nerve-cord into the vagina. 



In another specimen the entire uterine system lies to the left of the intestine and 

 neither uterus passes below the intestine from one side of the body to the other. In 

 this individual also the distal portions of the ascending uteri embrace and loop round a 

 bend of the right descending uterus (Fig. 15). 



There is some evidence to show that, accompanying parturition, either simultaneously 

 or subsequently, a resorption or reconstitution of that section of the uterus from which 

 an embryo has been liberated, takes place. In addition to direct signs of shortening in 

 the terminal (vaginal) region of a uterus, there is the fact that in one female 42 mm. 

 long the uteri extended 15 mm. from the posterior end, while in another which 

 measured 40 mm. in length, the uteri extended 275 mm. from the posterior end. 

 Evidence of resorption of the uterus after parturition is also shown by the fact that 

 partially pigmented embryos occurred behind the nearly ripe embryos shown in Fig. 12. 

 Whereas in other cases non-pigmented embryos occur next to the vagina — thus de- 

 veloping in situ. Finally the terminal narrow portion of the uterus lying between the 

 oldest embryo and the vagina, is of varying length. In the Neotropical forms, Kennel 

 has given reason for supposing that a permanent shortening — i.e. resorption — of the uterus 

 is a necessary phenomenon in parturition. An analogous phenomenon has been observed 

 in widely different animals, e.g. Salpa. 



Male Keproductive Organs. 



It is in the constitution of the male reproductive organs that P. novae-britanniae 

 exhibits what is perhaps its most distinguishing anatomical characteristic. 



The tubular, more or less hook-shaped, testes debouch into the large ellipsoidal 

 seminal vesicles, as usual at one side of the latter some distance from the anterior tip. 

 The coiled vasa efferentia emerge from the seminal vesicles from a point on the opposite 

 side some distance from the posterior tip. The coiled vas efferens of each side proceeds 

 backwards for a certain distance, when the coils cease and the duct is continued on 

 each side as the straight vas deferens to the extreme posterior region of the body 

 (Fig. 19). Arrived there, each vas deferens passes under the corresponding nerve-cord 

 and then the two meet together in the middle line to form the median ductus 

 ejaculatorius (Fig. 20). Thus the unpaired portion of the male duct is hardly any 

 longer- than the vagina. Its actual length would hardly exceed 15 mm. including the 

 projecting papilla. 



