202 WAGENER, ON GYRODACTYLUS ELEGANS. 



The intestine of Gyrodactylus, which is bifurcate and 

 csecal^ communicates with the pharynx by a short oesophagus, 

 and is of uniform structure throughout. In individuals as 

 yet uninjured by examination^ the central space of the intes- 

 tine and of the oesophagus is filled with a clear fluid, by 

 which the walls are kept asunder. I have never seen this 

 fluid resembling blood, as it does in Dactylogyrus monenteron. 

 In the large, beautiful Gyrodactylus of the loach, the 

 intestine was always charged with a clear, yellowish fluid, 

 which served the purpose of an injection in the examination; 

 in appearance this fluid resembled the yellow, homogeneous 

 pigment by which the integument of the fish is coloured. 



Two layers may be distinguished in the intestinal tube ; 

 the outer of which is, in appearance, structureless. The 

 inner is much the thicker, and consists of a uniform layer 

 of a fine, granular substance, in which, here and there, 

 transverse lines may be observed, which appear to indicate a 

 cellular structure. In general this layer is soon broken up, 

 and it then fills the intestinal canal. The course of the in- 

 testine is exactly the same as in many Distomata. It runs 

 on the sides of the body immediately beneath the dorsal 

 surface. The two csecal sacculi meet in the middle line, 

 making a short turn in order to eSect the junction. The 

 distance apart of the somewhat enlarged extremities of the 

 intestinal canal depends upon the degree of distension of the 

 uterus. In length it occupies about the two middle fourths 

 of the animal. It embraces the ovum, the uterus, the testis, 

 and rests upon the ovary ; the upper enlargement of which, 

 however, projects somewhat beyond it, on the outer side. 



The vascular system is found not on the dorsal, but on the 

 ventral side of the body. Its thin walls inclose a clear fluid, 

 and the finer branches are furnished with distinct ciliary 

 lobes. Four principal trunks may be seeft lying in pairs on 

 either side of the animal, close together, and corresponding 

 with each other in their course. 



In the caudal portion of the animal, near the upper bol-der 

 of the suctorial disc, and close below the ovary, the two pairs 

 of vessels turn towards the mesial line. The two corres- 

 ponding superficial vessels from each side join to form a short 

 but not larger trunk, which bends so abruptly from the 

 observer as to present a perfect transverse section. Whether 

 it perforates the wall of the abdomen, or opens on the dorsal 

 surface, as may well be supposed, could not be made out. 



The other two corresponding vessels on each side, which, 

 on the whole, are less distinctly seen, are apparently lost 

 in more slender branches, which, together with branches from 



