1909. | BLOOD-PARASITES OF FRESHWATER FISHES. 23 
the nuclear structure, since in the smears which I stained with 
iron-hematoxylin I was unable to find any trypanosomes, though 
Trypanoplasma gurneyorum was abundant. 
4. TRYPANOSOMA TInca Lav. & Mesn. (Plate II. figs. 27-29 ; 
Plate IV. figs. 74-76). 
The trypanosome of the Tench was described and named by 
Laveran and Mesnil (Trypanosomes et Trypanosomiases, Paris, 
1904, pp. 387, 388, fig. li. 2 & 3). Its occurrence had been 
noted previously by Doflein (Die Protozoen als Parasiten etc., 
Jena, 1904, p. 71), and since then by Keysselitz (Arch. Protist. 
vil. 1906, p. 3). Doflein considered that the parasite seen by him 
might be identical with Trypanosoma carassii from Carassius 
vulgaris, but Laveran and Mesnil regarded it as a distinct and 
new species, and described it as follows :— 
* La longueur est de 35 4 en moyenne, la largeur de 24 4a 3 
L’extrémité postérieure est conique, peu effilée. Le centrosome, 
assez gros, est voisin de l’extrémité postérieure. Le noyau est situé 
vers la partie moyenne du corps du parasite. La membrane on- 
dulante est large, bien plissée. La partie libre du flagelle est 
assez longue.” 
I found trypanosomes in all tench examined by me at Sutton 
Broad, occurring together with Zrypanoplasma keysselitzi, and 
have observed nothing to prevent me identifying them with 
Trypanosoma tince of Laveran and Mesnil. This trypanosome 
appears to be very uniform in size and structure, so far as my 
observations extend ; the two specimens figured by Laveran and 
Mesnil differ somewhat in size. In my never-dried preparations 
fixed with Schaudinn’s fluid, with or without previous fixation with 
osmic vapour, and stained with iron-hematoxylin (figs. 74-76), 
the trypanosomes appear constantly smaller than they do in pre- 
parations fixed wet with osmic vapour, or dried before fixation, 
and stained with Giemsa’s stain; but I attribute this difference to 
the effects of the method of fixation. 
In osmic-fixed preparations the trypanosome shows, as Laveran 
and Mesnil have stated, a very broad undulating membrane, 
standing out well from the body, and continued into a free 
flagellum of moderate length (figs. 28, 29, 36); the cytoplasm is 
opaque in such preparations and usually shows numerous coarse 
granules, which stain reddish with Giemsa’s stain, and by the 
iron-hematoxylin method appear black and hold the stain fast. 
The kinetonucleus appears large after Giemsa; but very much 
smaller after iron-hematoxylin, and by the latter method shows 
two types of form, rounded and rod-shaped (figs. 74-76). The 
blepharoplast is not easily seen in the Giemsa preparations, 
owing to the opacity of the cytoplasm, but in iron-hematoxylin 
preparations it appears as a sharp dot near the kinetonucleus. 
The trophonucleus appears after Giemsa stain as an oval patch 
showing no details of structure ; after iron-hematoxylin it appears 
as a rounded or oval space, not very sharply limited, containing 
