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VIII., fig. 19), closely resembles, in its generally flattened, 
bean-shaped contour, the cosmopolitan, free-swimming species 
Chilodon cucullulus . It is wanting, however, in the complex 
buccal armature that distinguishes that species, while the sepa- 
rate fringe of adoral or peristomial cilia is much more power- 
fully developed. The habitat of this animalcule is identical 
with that of Trichodina pediculus , it occurring as an ecto- 
parasite, often in vast numbers, on the body and tentacles 
of Hydra vulgaris and other fresh-water polypes. Like these 
Trichodinse, it does not actually prey on the living tissues of its 
selected host, but contents itself with the waste material cast 
off from the cuticular surface, acting thus rather as a useful 
and efficient scavenger than as a parasite in the stricter and 
limited significance of that term. 
EXPLANATION OF PLATES. 
Plate VII. 
Figs. 1 and 2. Trypanosoma sanguinis, Gruby. Parasite of blood of Frogs, 
x 600. 
Figs. 3-5. Trypanosoma Eberthi, S. K. Parasite of intestinal viscera of 
ducks and geese, x 800. 
Figs. 6-8. Herpomonas muscce-domesticte, Burnet, sp. Intestinal parasite 
of common House-fly. At Fig. 8, example dividing by longitudinal 
fission, x 650. 
Figs. 9 and 10. Herpomonas Leioisi, S. K. Parasite of blood of Indian Rats. 
x 800. At 11, blood corpuscle of Rat similarly magnified for pur- 
pose of comparing relative size. 
Fig. 12. Rhaphimonas Butschli, S. K. Intestinal parasite of nematoid Worm, 
Trilobus gracilis, x 600. 
Fig. 13. Bodo intestinalis, Ehr. Intestinal parasite of Frogs and Toads, 
x 300. 
Figs. 14 and 15. Lophomonas blattarum, Stein. Intestinal parasite of Cock- 
roach, Blatta ( Periplaneta ) orient alis, elongate and subspheroidal 
forms, x 500. 
Fig. 16. Asthmatos ciliaris, Salisbury. Parasite of nasal and respiratory 
passages of the human subject, x 600. 
Fig. 17. Trichomonas batrachorum , Perty. Intestinal parasite of the Frog, 
x 650. 
Figs. 18-20. Hexamita intestinalis, Dujardin. Intestinal parasite of Frogs 
and Toads. 18 and 19, attached; 20, free-swimming conditions, 
x 800. 
Figs. 21-25. Opalina ranarum, Purkinje. Intestinal parasite of Frogs and 
Toads. 21, multinucleate adult animalcule, x 100 ; 22, zooid divid- 
ing by transverse fission ; 23, sporocyst with contained zooid ; 
24 and 25, young mononucleate condition. 
