ZOOLOGY AND BOTANY, illCROSCOPY, ETC. 49 



margins of the body ; the mouth is placed at the bottom of the 

 anterior sucker, but has an anal in addition to an oral function ; the 

 ingestive and digestive regions of the interior are very distinctly 

 marked off from one another. The oesophageal portion is well pro- 

 vided with muscle, and the whole anterior region is well adapted to 

 act as a sucking organ. Protractor and retractor muscles are further 

 attached to the pharynx. By the especial action of the latter the 

 pharynx is filled, then the cii'cular muscles of the pharynx contract, 

 and the nutriment is driven into the stomach or digestive portion. 

 This, which is at lii'st unpaii-ed, soon divides into two lateral branches, 

 and from these sixteen or seventeen processes are given off. After 

 describing the arrangement of these offshoots, the author proceeds to 

 the histology of this part of the tract, in which he finds an outer layer 

 of connective substance (a layer of contractile elements could not be 

 observed, although Leuckart has reported its presence), and an inner 

 layer of enteric epithelium, which is simple, and made up of cylindrical 

 cells of varying heights. The characters which these cells present 

 compel the author to compare them to the nutrient individuals of a 

 Hydroid colony. A characteristic figure is given to illustrate their 

 mode of seizing on the food, in which the irregular projection of their 

 protoplasmic contents is very well sho^Ti. 



Under the head of the excretory system the writer gives an account 

 of a system which, not only in its physiological relations, but also in 

 its structural characteristics, calls to mind the lymphatic system of 

 the Vertebrata. This system does not, however, communicate with 

 the heemal, but passes its final or uric products to the exterior. It is, 

 in fine, a system which, while it resembles by its characters and 

 distribution the lymphatic system of the Vertebrata, differs from it, 

 and resembles the excretory organs, in opening on to the surface of 

 the body. The tubes can best be made out by filling the system which 

 they compose with colouring matter, and this can be introduced by 

 the excretory pore, or, still better, by injection. The system consists 

 of the ducts in the tissues and the collecting vessels. The former 

 especially arise in the substance of the median layer ; the tubes unite 

 into a collecting plexus, which is concentrated at the boundary 

 between the median and cortical layers ; the ducts given ofi" from this 

 anastomose and so form a second plexus. No valves, nor any layer of 

 muscles with a special expulsive function can be mada out in any part, 

 or even in the terminal trunk. The tubes contain a coloui'less fluid 

 with small refractive globules. According to Leuckart, guanin was 

 detected by Lieberkuhn in the contents of these vessels. 



The nervous system is very difficult to make out, owing probably, 

 as Leuckart has suggested, to the absence of any perineurial invest- 

 ment. As an aid to research it is well to place the animal in carmine, 

 then to treat it with alcohol, and finally to clarify it ; sections must 

 also be made. The central portion consists of a nerve-ring around 

 the pharynx, which is enlarged at three points by the deposition of 

 ganglionic cells. Two of these, which are bilaterally symmetrical, 

 lie just behind the sucker, and form the supra-oesophagea,l ganglia ; 

 the third may be regarded as the sub-cesojihageal ganglion. The two 



Ser. 2.— Vol. J. E 



