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III . — Observations on the Structure of the Red Blood- corpuscles 
of living Pyrensematous Vertebrates. By W. H. Hammond.* 
In my last paper on the structure of the living blood-corpuscles 
of a young trout, I pointed out that a nucleus could be plainly 
seen with a power of a little more than 300 diameters. I have 
since then extended my observations to the structure of the same 
corpuscles in the blood of other vertebrates. My first observation 
was made on a very young duck, and in this bird I was able to see 
the blood as it flowed in a small vein or capillary just at one part 
of the web of the foot. I could see plainly with the same power as 
before that the red blood-corpuscles are circular, with a distinct 
nucleus, which could be plainly seen both when the corpuscles ex- 
posed their broad surfaces, and also when they were sideways. 
These corpuscles have no cylindrical ring, but are flat from the 
nucleus to the circumference. My next observations were made on 
a living minnow and roach ; the corpuscles are just like those seen 
in the young trout with a nucleus, clearly seen with the same power 
as before. In the living stickleback I noticed that the corpuscles 
are smaller than those seen in the trout (as is shown in Professor 
Gulliver’s Tables), but of the same shape, and the nucleus is as 
plainly visible. On another occasion I watched the circulation 
in some young tadpoles and newts. In the very young tadpole I 
noticed that the red corpuscles were covered with small round bodies 
looking like vesicles ; the corpuscles were oval when their broad 
surfaces were exposed, and appeared lanceolate when seen side- 
ways. The corpuscles seemed very elastic, and were easily squeezed 
out of and resumed their shape when turning a corner. In the 
small blood-vessels in which the corpuscles flowed in single file, I 
had a good view of the “ tailing out ” of the corpuscles ; but, with the 
same power as before, I could not make out any nucleus, though 
several times I thought I saw a faint appearance of it. In an older 
tadpole, which had two legs formed, 1 noticed that the corpuscles 
had fewer vesicles on them ; in other respects they were the same 
as in the younger ones. In a frog’s foot the corpuscles had no 
vesicles on them. 
I then tried to see the circulation under a high power in the 
tadpole of the frog, in the newt, and in the frog’s foot. I used a 
| th objective with B, C, and D eye-pieces, and am happy to say that 
1 was successful. I could with this high power see a nucleus in 
* It would be well if the author of this paper would refer to the splendid 
researches of Strieker, Schweigger-Seidel, Max Schultze, and Briicke, the last 
of whom describes the mammalian blood-globule as consisting of two separate 
parts, the zooid and the oekoid. It may be remarked that Mr. Hammond’s 
researches have this especial value, that they arc confined to the living corpuscles 
of pyremematous vertebrates. 
