• DR. T. S. COBBOLD ON ENTOZOA. 169 



Trematoda. 

 Fasciola gigantica, T. S. C. Distoma clavigerum, R. 

 ■ hepatica, Linn. cylindraceum. Zed. 



Campula oblonga, T. S. C. fulvum, R. 



Hemistomum spathula. Dies. gracilescens, R. 



Echinostomum spinulosum, R. hispidum, Abildy. 



Monostoma caryophyllinuni ?, Zed. rachion, T. S. C. 



dubium, T. S. C. Polystoma integerrimum, R. 



Distoma atomon, R. 



The names here abbreviated are those of Rudolphi, Bremser, Dujardin, Diesing, Linneus, Zeder, 

 Creplin, Frolich, and Abildgaard. 



DESCRIPTION OF THE PLATES. 

 Tab. XXXI. 



Fig. 1. Tcenia filicollis. Natural size. 



Fig. 2. Monostoma caryophyllinuni, imperfectly developed. Natural size. 



Fig. 3. The same, showing an oral sucker and cells in the interior. Magnified 300 diameters. 



Fig. 4. Monostoma dubium (mihi). Natural size. 



Fig. 5. The same, displaying the elongated ventral appendage and internal gastric cjeca. Enlarged 200 

 diameters. 



Fig. 6. Four examples of i)i«/oma /?</««;». Natural size. 



Fig. 7- One of the above, showing the position of the suckers and the extremely attenuated neck during 

 elongation. Enlarged 20 diameters. 



Fig. 8. The same, during contraction ; it also exhibits the intromittent organ and ova within the uterine 

 tube. Magnified 60 diameters. 



Fig. 9. Three specimens oi Distoma rachion (mihi). Natural size. 



Fig. 10. One of the above, enlarged 40 diameters. It exhibits the regularly arranged dermal spines 

 investing the whole of the body ; an oral and ventral sucker, the lining membrane of the former 

 consisting of polygonal cells; a narrow CESophagus communicating with a broad, elongated, 

 horse-shoe-shaped digestive cavity — in front of the latter a wide uterine tube symmetrically 

 disposed in coils on either side and filled with ova; and an internal seminal vesicle. The ovary 

 is placed immediately above the caudal vesicle, and is surmounted by the testes. 



Fig. 11. Transparent cyst from the subperitoneal surface of the intestine of a Haddock. Natural size. 



Fig. 12. The same, ruptured. Magnified 4 diameters. 



Fig. 13. Scolex of Tetrarhynchus, escaped from the cyst. It shows the head and body enveloped by the 

 large caudal vesicle, the surface of which is slightly segmented and dotted by the highly refracting 

 sclerous particles. Magnified 4 diameters. 



Fig. 14. The same with the body and proboscides evolved. Natural size. 



Fig. 15. Part of the Scolex, enlarged 20 diameters. It exhibits the four narrow and pointed phylloid 

 bothria, a portion of the transparent caudal vesicle with its sclerous particles, and more particu- 

 larly the four proboscides, two of which are partially withdrawn from their sheaths. 



Fig. 16. An oval sclerous particle, magnified 200 diameters. 



Fig. 17. Section of a proboscis or tentacle, showing the peculiar arrangement of the hooks and booklets. 

 Magnified 200 diameters. 



