458 Royal Society : — 



ally widening towards its posterior border, which is exceedingly 

 thin. The outer integument is perfectly transparent and lined by 

 muscular bundles, disposed longitudinally, and somewhat more than 

 their own breadth apart. These communicate with one another by 

 oblique branching slips, which thus form a kind of network enclosing 

 long lozenge- shaped spaces. Here and there nerve-trunks of con- 

 siderable size accompany the longitudinal bundles, dividing off into 

 smaller twigs, which distribute themselves at pretty equal distances 

 in a direction more or less perpendicular to that of the muscular 

 fibres. Scattered about at irregular intervals amongst these struc- 

 tures are numerous reddish-brown pignient-spots, in the centre of 

 each of which a clear vesicle is generally distinguishable. As above 

 alluded to, the actual tint of this pigment, and the relative number 

 of spots deposited within a certain space, determine both the general 

 quality and the depth of colour which are found to vary so much in 

 different specimens of PhyUirrho'e. 



The alimentary canal of this creature consists of a muscular tube 

 lined with mucous membrane, extending without lle.\ure from the 

 mouth to the vent. It commences anteriorly in an oral dilatation, 

 in connexion with which we notice a pair of lateral horny jaws arti- 

 culated with each other sujieriorly, and beset with very minute and 

 sharp-pointed teeth along tbe cutting edge, altogether much resem- 

 bling those of Glaucus, and a lingual ribbon gradually increasing in 

 diameter from l)efore backwards, and supporting a pavement of long, 

 conical, flattened and gracefully curved teeth with fine denticula- 

 tions at the base. The central series of jilates being symmetrical, 

 the large tooth in each takes up a middle position, but in the lateral 

 plates it inclines to the inner side. In some examples I have ob- 

 served certain lobulated bodies lying in contact with the buccal 

 mass, and which I am disposed to regard as salivary glands. The 

 CESophagus is short, and suddenly expands into a moderately large 

 stomach; and the latter, having received the biliary ducts near its 

 posterior extremity, is continued into the rectum, which passes 

 directly backwards some little distance, and ends in the anus, on the 

 right side of tlie body, at the union of its jjosterior and middle thirds. 

 The liver in PhyJlirrhot consists of four elongated, tubular, and sac- 

 culated portions or lobes, disposed along the borders of the body, 

 two lying above and two below the alimentary canal. Each of the 

 superior hcj)atic glands opens by a distinct duct into the supero- 

 posterior part of the stomach, while the ducts of the inferior ones 

 unite to form a comm.on tube joining it at its infero-])Osterior part. 

 The opposite or ca-cal extremities of the two anterior he])atic lobes 

 end in the neighbourhood of the head, while those of the others 

 extend to within a short distance of the tail. The secreting cells of 

 these organs are of a rounded or polyhedral form, containing, be- 

 sides the nucleus, a reddish-brown pigment and fatty globules. 



jP/iy////v/ioe possesses a simple systemic heart, consisting of a single 

 auricle and ventricle. This organ lies upon the stomach, between 

 the ducts of the two sujierior biliary glands ; and a large vessel or 

 sinus, with many circular constrictions in its walls, may be traced 



