ON WANDERING CELLS IN ECHINODERMS. 83 
was attempted with defibrinated rat’s blood, but these latter 
did not give any results worth recording here.) The Indian 
ink was injected with a hypodermic syringe into the abdomen ; 
an examination of the blood fluid soon after showed that many 
of the ameboid blood-corpuscles had taken up one or more 
particles of the Indian ink, which gave the fluid a dusky, dirty 
appearance to the naked eye. Even after the lapse of a 
month (thirty days) there were found to be still some free 
granule-containing leucocytes, though not so abundant as at 
earlier periods. 
What interests us here is that, in specimens which have 
been kept for some time after the injection (e.g. ten days to 
thirty days), there were seen to he small black specks, visible 
to the naked eye, which were scattered about in different 
regions of the body, especially about the heart and the more 
dependent parts of the abdomen. When examined under a 
low power each dot was found to consist of a central mass of 
black carbon particles surrounded by a clear zone formed of 
nucleated cells, some of which also contained granules of 
carbon. 
It might be said that these collections of pigment and cells 
were usually close to or attached to the tracheal tubes, were it 
not that these structures are so ubiquitous in their distribu- 
tion; they are mostly of spherical shape after ten days or 
thereabouts, but after longer periods they may become larger 
and more elongated, losing the spherical shape by the addi- 
tion of fresh cells with carbon particles (fig. 1). These small 
masses originate about a centre which may begin as an acci- 
dental collection of carbon particles which have become 
stranded close together, and become afterwards invaded more 
or less by leucocytes ; or the carbon particles may be first 
ingested by leucocytes which subsequently come together ; in 
both cases other leucocytes, either with or without carbon 
granules, become adherent to the mass and add to its size. 
After getting attached to the mass they become flattened and 
appear crescentic in section, the nucleus appearing elongated ; 
thus a capsule is formed round the mass. 
