214 Transactions of the 



situated one on each side of and in close juxtaposition to the com- 

 mencement of the rectum. These tubes are more visible in the 

 largest specimens ; indeed, in the smaller ones they are scarcely per- 

 ceptible : this might account for my having miased seeing them in 

 my former observations. 



I tried feeding some vigorous specimens with indigo, and found 

 that the particles entered the pharynx through the branchial aper- 

 tures in a regular stream ; the greater part went out again through 

 the mouth, but the part which struck against the neural wall of the 

 pharynx turned back, and were carried by the ciliary current into 

 the oesophagus and thence into the stomach, and eventually into the 

 remainder of the intestine ; the indigo followed this course in every 

 instance in which the experiment was tried. 



Digestive System. — This species of Oikopleura is distinguished 

 by the high development of its alimentary canal. ? 



The general description of this tract was given in the former 

 paper ; I will content myself, therefore, in this place with adding 

 some further details to that account. 



The mouth looks towards the neural surface ; it is heart-shaped, 

 being provided with a rounded anterior lip. 



The stomach is a complicated organ ; it consists of two flattened 

 disk-like lobes, one of which lies parallel to the right side of the 

 body, the other lobe is situated at right angles to this on the neural 

 side ; it is this latter part that I termed the first portion of the 

 intestine, from the fact that faeces begin to be observable therein ; but 

 as most authorities appear to consider it to be a lobe of the stomach, 

 I shall adopt that view|in future. The two lobes in A.jlahellum are 

 described by Professor Huxley * as being parallel, and not at right 

 angles, as in this specimen. The right lobe of the stomach, which 

 corresponds to the left lobe in Dr. Fol's nomenclature, is provided 

 with two different species of cells in the hning membrane ; one sort 

 are large, and form hemispherical projections into the cavity of the 

 stomach ; these are arranged in a crescentic form, and occupy that 

 part (about half) of the mucous membrane which is situated towards 

 the haemal side of the body ; the space between the right and left 

 walls on this side is occupied by four or five cells much larger than 

 the remainder. 



The other portion of the mucous membrane of the right lobe of 

 the stomach is formed of flat irregularly polygonal cells, which 

 occupy the spaces between the above-mentioned rounded cells, and 

 also spread over that wall of this lobe which is directed towards the 

 neural side ; these flat cells vary in shape and size ; they line the 

 whole of the right lobe not occupied by the rounded cells. The 

 transition between the right and left lobes is marked by a longi- 

 tudinal ridge at the angle which they form together, but the 



* Loc. cit. 



