Royal Microscopical Society. 147 



shape and of about the same size ; this is placed transversely across 

 the posterior end of the body ; the aperture of communication 

 between the two is very distensible, although not at all apparent 

 when nothing is passing. The faeces are made up into oval masses 

 by a material of some considerable tenacity, and I have watched 

 these masses pass from No. 1 to No. 2, and vice versa, for some time 

 without their breaking or becoming mixed up with each other ; as 

 they passed lengthwise the opening at last became so large that the 

 cavities of the two chambers seemed thrown into one. I concluded 

 that these masses moved backward and forward because No. 3 being 

 full they could not get any farther. 



The third chamber emerges from the anterior wall of the dorsal 

 end of No. 2, and passes forward parallel to and in contact with 

 No. 1 ; it is of an oval form, and appears to be provided with the same 

 kind of parietes as the other two. I have not actually observed the 

 passage of faeces between No. 2 and No. 3, but on one occasion I 

 happened to observe that No. 2 was full while No. 3 was empty. A 

 short time after, on again looking at the animal, the case was re- 

 versed, for then No. 3 had become full and No. 2 was empty. 



The fourth compartment might be denominated the rectum ; it is 

 continued in the same direction as No. 3, but in a line shghtly moved 

 towards the anterior extremity ; it communicates with No. 3 at a point 

 which is rather on the ventral side of its anterior end. This chamber 

 also is oval, has thick walls, and terminates in the anus, which is a 

 small papilla situated just in front of the attachment of the append- 

 age. As in Gegenbaur's specimen, the anus appears to open between 

 the wall of the body and the mantle, but that there is an opening 

 through the latter, although not visible, is certain, for the faeces were 

 seen to pass through the anus and the mantle into the surrouudiuo- 

 medium. The intestine in these specimens is seen to be more com- 

 plicated than in the species described by Professor Huxley and 

 Professor Gegenbaur, as their figures only show a simple nearly 

 straight tube running between the stomach and the anus. 



With regard to the circulatory system, I could find no indica- 

 tion of a heart. I cannot imagine if it had been present in these 

 animals that it would have escaped notice, although according to 

 Professor Huxley it is very difficult to be seen in A. flahellum, in 

 which species it is situated between the two lobes of the stomach 

 and the insertion of the appendage, a space which in my examples 

 is occupied by the intestine. 



The otolithe is a very conspicuous object occupying the centre 

 of a transparent vesicle on the ventral side of the body ; this is sur- 

 rounded by the graniilar nervous ganglion, from the posterior end 

 of which a nerve runs downward over the right side of the oesopha- 

 gus until it reaches the stomach, where it becomes lost to view ; 

 anteriorly the ganglion is prolonged towards the anterior extremity 



