220 Mr. II. C. Williamson on a Bifid Earthworm. 



each an anus, and to all appearances were exactly similar. 

 The trunk and appendages were of nearly equal diameter 

 (PI. X. fig. 1). Bell does not say whether the specimen 

 described by him had two ani or not. The right-hand ap- 

 pendage was perhaps a shade less in diameter tiian the left. 

 In this respect this specimen differs from that described 

 by Fitch, in which the posterior appendages were of the 

 same thickness, but of less diameter than the anterior 

 portion. It differs also from that described by Robertson 

 (fig. 8), which appears from his drawing in that respect 

 to agree witli Fitch's specimen. When the worm was 

 placed with the dorsum upwards (fig. 1) it was found that the 

 anterior part marked AD, stretching from the prostomiura to 

 the fifty-fourth segment, where the bifurcation commenced, 

 was Ij'f, inch long, the left appendage, DB, 1|| inch long, and 

 the right appendage, D'C, IfV inch long. In the portion 

 AD there were 54 annuli, in DB 122 annuli, and in D'(J 

 109 annuli. The specimen when examined was in spirit and 

 to some extent contracted. The dorsal line was visible 

 in the anterior portion, in which it could be traced up 

 as far as the nineteenth segment. It ran in a perfectly 

 continuous line down the trunk and the left appendage 

 to the anus (fig. 1). No trace of it could be made out in 

 the right appendage. This is the first important difference 

 between the tv/o appendages, and leads one to suppose 

 that the trunk and the left appendage form the complete 

 worm, and that the right appendage, in which there is no 

 trace of the dorsal line, is the extra portion. Fitch was 

 led to the same conclusion in his specimen. 



On examining the junction of the three parts it was seen 

 that the right appendage D'C arose from the right lateral 

 portion of the fifty-fourth segment (fig. 2). The origin of 

 this appendage differs from that of the corresponding one in 

 Robertson's s])ecimen (fig. 8), neither does it occur by the 

 bifurcation of the fifty-fourth segment. At its junction with 

 the filty-tburth segment the right appendage is constricted. A 

 similar constriction was noticed in the right appendage of 

 Fitch's specimen and also in one of the appendages of the 

 ea)thworm recorded by Marsh. On dissection it was found 

 that the dorsal blood-vessel was bifurcated, as also were the 

 gut (fig. 3), the supra-noural vessel (fig. 5), and the nerve- 

 cord (fig. -1). The typical double nerve-cord was present in 

 the anterior and both posterior portions. There was no 

 appreciable difiorence in diameter between the two posterior 

 portions of the dorsal blood-vessel ; the intestine in the right 

 aj)pendage was, however, a little less in diameter than that 



