364 
Crithidia gerridis 
Patton, W. S. and Strickland, C. (1908). A critical review of the relation of 
blood-sucking Invertebrates to the life-cycles of the Trypanosomes of Vertebrates, 
etc. Parasitology , I. pp. 322—346. 
Swingle, L. D. (1909). A Study on the Life-History of a flagellate (Crithidia 
melophagi , n. sp.) in the alimentary tract of the sheep-tick ( Melophagus ovinus). 
Journ. Infect. Diseases, vi. pp. 98—121, 3 plates. 
EXPLANATION OF PLATE IV. 
All figures were outlined with an Abbe-Zeiss camera lucida, using a 2 mm. apochro- 
matic or ^2 inch achromatic (Zeiss) objective and compensating ocular 8 
of Zeiss. 
The magnification is, in all cases, approximately 1300 diameters. 
Fig. 1. Pre-flagellate, recently ingested. Nucleus shown to one side, blepharoplast 
distinct. Crop of Gerris Nymph. Delafield. 
Figs. 2—4. Larger pre-flagellates than in 1. Crop preparation. Giemsa. 
Fig. 5. Pre-flagellates with blepharoplast in contact with nucleus. Crop of adult. 
Giemsa. 
Fig. 6. Pre-flagellate showing very early development of flagellum from the neighbourhood 
of the blepharoplast. Flagellum lying close to the body. Crop of adult. Gentian 
violet. 
Fig. 7. Parasite with longer flagellum. Crop of adult. Giemsa. 
Figs. 8—10. Parasites showing still longer flagella coiled on the body but not yet free 
from it. Crop of adult. Giemsa. 
Fig. 11. Small form with flagellum free from the body. Crop of adult. Giemsa. 
Fig. 12. Oval pre-flagellate showing the commencement of the elongation of the posterior 
end. Crop of nymph. Giemsa. 
Fig. 13. Very rounded and large form of pre-flagellate, with round blepharoplast. Crop 
of adult. Delafield. 
Figs. 14, 15. Late pre-flagellates showing progressive elongation of the posterior end. 
Crop of adult. Giemsa. 
Figs. 16—19. Stages in the division of pre-flagellates. Crop of nymphs. 
Fig. 16. Undivided form of parasite. Large specimen. Nucleus round, blepharoplast 
entire. Flagellum coiled on body. Thionin. 
Fig. 17. Young dividing form. Blepharoplast almost constricted in two; nucleus bilobed; 
flagellum split at the body end. 
Fig. 18. Division almost completed. The organism shows two blepharoplasts, two 
nuclei, two flagella, and a clearer area marks the line along which separation of the 
bodies of the daughter forms occurs. 
Fig. 19. Division of pre-flagellate as seen at a different plane from that shown in Fig. 17. 
Crop of nymph. Delafield. 
Fig. 20. Multiple longitudinal division of small pre-flagellates showing resultant rosette 
formation. Crop of nymph. Gentian violet. 
Fig. 21. Small flagellate. Nucleus and blepharoplast well shown. Stomach of adult. 
Gentian violet. 
