1909. ] BLOOD-PARASITES OF FRESHWATER FISHES. i 
a simple black rounded mass. J am of opinion that what he has 
figured is simply the karyosome, and that the peripheral portion 
oe the nucleus is not shown. The nuclear space and membrane 
are often not at all distinct, as I have said above, and I 
have often seen the trophonucleus appearing just as Liihe has 
figured it. 
In the cytoplasm there are commonly numerous coarse granu- 
lations, which stain like chromatin after Romanowsky, but I feel 
strong doubts as to their being chromidial in nature. After 
iron-hematoxylin I found that the granules gave up the stain 
much more readily than the true chromatic structures, in the 
trypanosomes ; but in the trypanoplasm of the pike they held the 
stain very tenaciously. Their true nature could only be deter- 
mined by the development. 
In the trypanosomes of the perch (figs. 96, 97) and eel (fig. 84) 
I was able to obtain preparations showing ‘the myonemes after 
the iron-hematoxylin stain. I have not been able to see myo- 
nemes in any trypanoplasm. J am convinced that to see the 
myonemes it 18 necessary to get just the right degree of extraction 
of the stain; a shade less extra action, and the myonemes are 
obscured by the darkness of the cytoplasm; a shade more, and 
the myonemes give up the stain. The darkly staining, opaque 
cytoplasm of the trypanoplasms probably makes it much more 
difficult to render visible the myonemes than in the case of the 
trypanosomes. From my preparations the myonemes appear to 
be about eight in number in the trypanosome of the eel, but more 
than that in the trypanosome of the perch. I have never been 
able to make them out with certainty after the Romanowsky 
stain. 
With regard to the question of the transmission of the trypano- 
somes and trypanoplasms of fishes, on which much light has been 
thrown by Brumpt and Keysselitz, I have only a few negative 
results to record. I found leeches very seldom on the fish caught 
by me; only once on a rudd, and once on a perch, a Piscicola was 
found attached, On the other hand almost every fish, of what- 
ever species, had Argulus attached to it when caught; sometimes 
there would be five or six Avguli on one fish. Argulus is stated 
in all the memoirs and text-books dealing with it to feed on the 
blood of fishes; it is an active swimmer, and readily leaves one 
fish and attaches itself to another. It seemed to me therefore 
that Argulus was a creature admirably suited by its habits to dis- 
seminate blood-parasites, either by the direct mechanical method, 
or witha cycle of development. Moreover, Argulus is beautifully 
transparent, and everything in its interior can be seen in the 
living animal under the microscope ; it is easy to focus its blood- 
corpuscles flowing through the heart and circulating in all parts of 
its body-cavity, or to see all the contents of its digestive tract, 
without injuring the beast in any way. It would be quite an 
ideal form in which to study the development and transmission of 
hemoflagellates. IJ took numerous Arguli, kept them hungry for 
