THE BLOOD OF MAGELONA. 13 
marked change in size; there is nothing approaching the 
gradual though rapid disappearance of the globules seen in 
the case of Magelona. 
Ultimately, though after a considerable time, the corpuscles 
appear to become dissolved, breaking up into granules. 
In Glycera, too, the corpuscles, as Claparéde, Lankester, 
and others have shown, are nucleated—the nucleus being oval 
and the corpuscle larger than that of Capitella. I was unable 
to obtain Glycera in any quantity, —in fact, I only came across 
two small specimens while collecting Magelona, and was unable 
to make many observations on them. But previous authors 
have compared these corpuscles with those of Vertebrates. 
The so-called “corpuscles” or coloured globules of Ma- 
gelona thus differ from the coloured corpuscles observed in 
other Annelids, not only in position, viz. within blood-vessels 
instead of in the ccelom, but also in structure and in their 
behaviour to chemicals, and I believe that they are different 
in constitution. 
These coloured globules in Magelona are to be compared 
with the coloured plasma of the ordinary Cheetopod blood, 
rather than with the coloured corpuscles of Capitella,Glycera, 
and Polycirrus. These globules, in fact, though recognisable 
as separate elements, do adhere together in the blood-vessels to 
form a fluid of the consistency of thick oil. If we suppose 
that a little more water were present in their composition we 
may imagine the globules to fuse with one another, and so form 
a more freely flowing plasma—such as is obtainable by ex- 
periment. This plasma would then be quite comparable with 
that of the blood of ordinary Annelids. But if we imagine the 
individual globules to have a firmer envelope—more resistent 
to reagents than it is in fact—we should have more perfectly 
defined corpuscles, comparable to the hematids in the blood of 
mammals. These adhere together, just as those of Magelona 
do, on being shed from the vessels. 
The globules of Magelona stand, as it were, midway between 
the coloured liquid plasma of Annelids generally and the 
coloured corpuscles of mammalian blood. The latter are 
