88 BNTOZOA. 



digestive canal, surrounded on all sides by sinuous foldings of the 

 ovarium, tuba, and uterus — the vagina terminating laterally at a 

 point corresponding with, the liae of the upper fourth of the body. 

 Here the male is usually found rigidly aflSsed by means of a strong, 

 membranous, sucker-like bursa, which proceeds from the lower 

 end of its body. This cup-shaped appendage is formed out of a 

 folded extension of the dermal covering, which thus envelopes the 

 centrally enclosed and rounded tail (4, fig. 22). The membrane of 

 the bursa is simple, transparent, undivided, smooth at its free 

 border, and strengthened internally by a series of projecting rays, 

 the precise number of which I could not ascertain with certainty. 

 Probably there were twelve ; but I only recognized nine. These 

 rays appear to me simple, firm, chitinous bands, whose purpose is 

 to fix and support the bursa, in the same manner as we find the 

 whalebone rods employed to distend the hood of an umbrella. 

 Acting antagonistically to these rays we also find a pair of strong 

 retractor muscles, which, taking their origin a little higher up on 

 either side, converge below to be inserted into the base of the 

 cup-shaped bixrsa (4, fig. 22). In addition to these structures, a 

 very distinct view of the penis can be gained by transmitted fight. 

 This organ, in the retracted condition, is entirely concealed within 

 the caudal prominence. It is very small, only about the 4 of 

 an inch in length, and consists of two narrow cylindrical spicules, 

 which, though distinct, are firmly united at their lower third. 



In regard to the pecuhar mode of union of the sexes, it becomes 

 an interesting point to ascertain whether there be an actual incor- 

 poration of the substance of the copulatory organs during or after 

 the act of impregnation. In my specimens none of the three pairs 

 were organically united, and I succeeded in separating one pair 

 very readily. Dujardin speaks of them as being soldered together, 

 whilst the statements of Von Siebold are still more expHcit. In 

 connection with this subject, the latter observer makes the 

 following comment :* — " The two sexes of almost all round worms 



* Wiegmann's ArcMv, 1836, p. 106. 



