14, W. BLAXLAND BENHAM. 
known not to be cells, but to be parts of cells, produced in 
many cases within cells by the modification of the protoplasm, 
its coloration and subsequent separation into globules, which 
are then set free by the breaking up of the parent cell. 
With regard to the development of the globulesin Magelona 
I have not yet come to any definite conclusion, though I 
expect to find that a similar origin of the corpuscles obtains.! 
The formation of the plasma in ordinary Annelids is practically 
on the same lines, but the fluid, in place of separating as 
globules or corpuscles, is discharged en masse (see Lankester’s 
observations “On the Connective and Vasifactive Tissues of 
the Medicinal Leech,” ‘Q. J. Micr. Sci.,’? vol. xx, 1880, 
p- 307). 
5. The Colouring Matter of the Blood.—We have 
already seen that no absorption bands were obtainable by means 
of the spectroscope, nor have I been able to separate any pig- 
ment by the use of various reagents. But from mere tint alone, 
and its change of colour on deoxidation, it is evident that the 
pigment is quite different from any hitherto recorded amongst 
the Chetopods; it is most evidently not hemoglobin. The 
other colouring matters known in the Chetopods are the greens 
of the Sabellids and Chlorhzmids, known as chlorocruorin. 
In no other Chetopod do we find the madder-rose colour 
characteristic of Magelona; but in Sipunculids a similar blood- 
pigment exists, presenting a similar loss of colour on deoxida- 
tion. This colouring matter, as seen in Sipunculus nudus, 
closely resembles that of Magelona. Its peculiarities were 
first described by Lankester,” and subsequently by Krukenberg,’ 
who gave to it the name ‘‘ Hemerythrin.” 
The blood-pigment in the Sipunculids occurs in the nucleated 
circular disc-shaped corpuscles of the fluid contained in the 
1 Miss Buchanan describes some of the early phenomena of the formation 
of the blood of Magelona (‘ Rept. Brit. Assoc.,’ 1895, p. 469), in which she 
suggests that the “corpuscles” arise from subdivision of multinucleate cor- 
puscles derived, apparently, from a special blood-forming organ in the dorsal 
vessel. 
2 Lankester, ‘ Proc. Roy. Soc.,’ xxi, p. 80. 
3 Krukenberg, ‘ Vergl. Physiol. Stud.,’ lst reihe, 3te Abth, p. 82. 
