440 APPENDIX. 



convoluted tubes, which were shortly afterwards united into a single one. 

 The single tube, after proceeding for some distance in a tortuous course, 

 became sacculated, and, enlarging as it descended, it terminated at the ex- 

 tremity of the tail in a trilobular aperture, the anus. On one occasion 

 I saw very clearly the opening and closure of this orifice. The com- 

 mencement of the alimentary canal by three tubes was not always 

 apparent, and for some time I imagined that it began by a single tube. 

 The motions of this canal were extremely beautiful. It moved freely in 

 the interior of the animal, at one time becoming straight and at another 

 time convoluted, as the body of the worm was extended or diminished. 

 It also moved backwards and forwards in an extraordinary manner, and 

 the sacculi were seen to close and dilate by a sort of peristaltic action. 

 On each side of the alimentary canal, at its commencement, there is a 

 series of lobulated bodies, the structure and office of which I could not 

 make out. They were of a light colour, and accompanied the oesophagus 

 in its lively movements in the longitudinal direction. In several male 

 worms a band was seen running along the centre of the intestinal canal, 

 being lost near the anus. 



" By the side of the alimentary canal, and sometimes crossing it obliquely, 

 I observed in many instances, especially in the female worms, a distinct 

 tube of a faint light colour, marked by transverse bands, which seemed to 

 have independent motions, somewhat of a pulsating character. It was 

 generally seen near the anterior part of the body, but it could be traced 

 for some distance towards the posterior. The pulsating character of this 

 tube was first determined by my friend Mr. Owen ; the pulsations occurred 

 at intervals of from eight to twelve seconds. This tube forms, in his 

 opinion, the analogue of the dorsal artery of the annelida. In several 

 worms I could distinctly perceive two light-coloured vessels twining round 

 the alimentary canal near the head, which gave off lateral branches, and 

 afterwards, joining, formed a single trunk, which also sent off branches 

 from its sides. Between the intestinal canal and external tegument 

 I could distinguish, on numerous occasions, an extremely rapid circulation 

 of minute globules, which passed in two contrary directions, side by side, 

 in a continuous stream. This was observed at intervals nearly the whole 

 length of the animals, being frequently obscured by the movements of the 

 digestive tube. I could also discern, near the tail, a number of globules 

 passing slowly in longitudinal and transverse currents, and crossing the 

 alimentary canal. 1 



" The structure of the female worm is much more complicated than that 

 of the male. The vulva is situated near the anterior extremity, about 

 one fifth of an inch from the head. It appears like a mamillated process, 

 is somewhat opaque, and can be discerned by the unassisted eye. The 

 animal swells at this part, the tegument is thicker, there are no spines, 

 and, for a short distance above and below the vulva, the body is encircled 

 by a series of regular, dark-coloured fibres. About mid-distance between 

 the head and vulva, and on opposite sides of the digestive tube, I inva- 



1 The worm became so opaque after immersion in spirit, and decomposed so rapidly, 

 that much of the beautiful organisation that I have described became lost to the observer 

 shortly after death. I attempted to preserve some in salt and water, and in dilute 

 vinegar, but without any better result. 



