BLOOD-PARASITES OF FISHES OCCURRING AT ROVIGNO. 145 



hsematoxylin films — that is to say, centrally or excentrically 

 is a comparatively clear, faintly stained area, while all the rest 

 of the nucleus is stained red more or less deeply (figs. 34, 35, 

 88, a-d), the periphery, in the neighbourhood of the mem- 

 brane, being perhaps darkest. The clear area corresponds 

 without doubt to the central part of the karyosome, i.e. to 

 the plastinoid basis free from chromatin. Rather curiously, 

 the central granule, referred to above as occurring in the 

 plastinoid part of the karyosome, is often very conspicuous, 

 probably because it is to a certain extent artificially enlarged 

 by the stain. The remarkable feature about these Giemsa- 

 stained nuclei, and the one which creates such a false impres- 

 sion, is that the nuclear sap is often so loaded with stain that 

 not only the rays but also the chromatic zone or ring imme- 

 diately surrounding the centi'al area is indistinguishable as 

 such. Occasionally, in more favourable pictures, the chro- 

 matic zone is more deeply stained than the nuclear sap and 

 can be distinguished somewhat better (fig. 37) ; and now and 

 then coarse indications of the rays proceeding to the periphery 

 can also be made out (fig. 38, h, c). Hence we have little 

 doubt that here also the structure of the nucleus agrees really 

 with that above described. 



Owing to the scarcity of Trypanosoma triglte in our 

 preparations the few individuals present on wet films do not 

 show the nuclear structure very satisfactorily. Extraction 

 had to be carried on quite in the dark, as it were, and neither 

 in the individual drawn in fig. 51 from a film stained with 

 iron-hsematoxylin, nor in that of fig. 65, from a preparation 

 stained with Twort, has the extraction been carried far 

 enough. From these two examples, however, it is quite 

 obvious that the nucleus is of the same karyosomatic 

 type, and fig. 51 affords indications that the structure of the 

 karyosome itself is similar to that above described. 



We regard the above instances as indicative of the typical 

 character, speaking broadly, of the nucleus of a heemogre- 

 garine and the trophonucleus of a trypanosome. 



So far as the case of the trypanosome is concerned, it is 



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