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II.—Observations on the Structure of the Red Blood-corpuseles of 
a young Trout. By W. H. Hammonp, Esq. 
THe circulation of the blood in a young trout may be so plainly 
viewed under the microscope, owing to the great transparency of 
the fish, that it occurred to me it would be a very good subject for 
experimenting on to ascertain if the red blood-corpuscles contain a 
nucleus in their living state as they flow in the vessels. By get- 
ting the little fish in a suitable position, as it swam in a cell full of 
water, I was able to use an objective giving an amplification of 
over 300 diameters; with this power I could see the corpuscles 
where they flow, slowly and singly, very distinctly in the smallest 
veins. When the red corpuscles presented their broad surfaces, 
they had the appearance represented in Fig. 1, a central spot or 
nucleus, and a rim round the margin. I also had good side views 
of the corpuscles in the small veins, just at the point where they 
branch out of the larger ones; here the corpuscles were continu- 
ally turning over, and at times one remained stationary for a little 
while ; when the edge was exactly opposite to me, they had the 
appearance shown in Fig. 2, the central spot or nucleus clearly 
projecting on both sides of the blood-disk. I could also see, as the 
corpuscles rolled over, that their outer part is a cylindrical ring; a 
section of one would have the appearance shown in Fig. 3. These 
observations were repeated many times on young trout varying 
from a day to three weeks old. 
Fiaq. 1. Fig. 2. Fig. 3. 
The question is\ important, for Professor Gulliver, F.R.S., 
in his paper entitled “Observations on the Sizes and Shapes 
of the Ked Corpuscles of the Blood of Vertebrates,” * says, “In 
every animal, without any known exception, of this great divi- 
sion (Pyrenemata), the red blood-corpuscle is characterized by 
the presence of a nucleus, which is plainly demonstrable in the 
majority of the corpuscles when examined on the object-plate under 
the microscope. Nor is the taxonomic value of this fact at all 
* «Proc. Zool. Soc., June 15, 1875. 
