320 The American Naturalist. [April 
places were found, or any trace of free carbon. Serial sections ~ 
made of the ureters (Pl. VI) close to their openings into the 
cloaca showed masses of ingested cells. This indicated that a 
considerable number of such cells found their way out of the 
body in this way. Uningested cells were also found among 
those containing carbon. In the liver (Pl. V) ingested cells 
were found in the blood vessels alone. No extra-vascular 
carbon-laden leucocytes were present. In the stomach (PI. VII) 
the carbon-laden cells were in the blood-vessels, in the epithe- 
lial tissue of the stomach and free on the inner surface, show- 
ing a gradual passage from the vessels to the epithelial surfaces. 
In the lungs (Pl. VI) practically the same time condition 
existed and also in the skin (P1. VII). In the latter leucocytes 
could be traced from the blood-capillaries through the various 
layers and finally free on the outer surface of the skin. That 
these outside had not come from accidental external contact 
was proved by the fact that no red corpuscles were among these 
leucocytes and with the very rapid coagulation that takes 
place in amphibian blood it would be impossible for the white 
cells to be completely isolated from the red. In various parts 
of the muscular tissue, either in the lymphatics or simply 
between the muscular fibres, ingested cells occurred rarely. 
In all these parts there was absolutely no evidence for the 
presence of free carbon or carbon in any other cells than 
leucocytes. When, however, the spleen (Pl. V) was examined — 
some peculiar and very interesting differences were found. 
The carbon was contained in leucocytes of a similar nature to 
those in previous cases, but in addition round the malpighian 
corpuscles there was what seemed at first sight to be a free de- 
posit of carbon. But when carefully observed the carbon 
proved to be contained in cells that from their position wet 
judged to be spleen-pulp cells. The distribution of the carbon 
in these cells differed exceedingly from that present in the 
leucocytes. Instead of being massed irregularly the carbon 
was evenly scattered through the cells, and, owing to the 
extended condition of the latter, covered a large area. hide 
the fact of the presenee of carbon in these cells was established 
the question of the means of the transfer of the carbon from 
