SEA-FISHERIES LABORATORY. 115 
being unaffected by acids, the materials used in fixation, 
by formalin or alcohol. It was unaffected by nascent 
sulphur dioxide, liberated by adding oxalic acid to a 
solution of potassium sulphite. It was bleached by the 
chlorine and oxides of chlorine liberated from a solution 
of potassium chlorate containing hydrochloric acid. 
It is not decolourised by weak alkali. It is bleached by 
hydrogen peroxide (commercial strength, ‘‘ 20 vols.’’) in 
two to three days, the deep black fading to a light yellow- 
brown colour. The sections bleached in acid chlorate 
solution were unsatisfactory since the colour appeared to 
return after the manipulation of the sections, and the 
staining reaction was not a good one. Decolourisation by 
hydrogen peroxide was employed in all cases prior to 
staining, but the tissues so bleached stained unsatisfac- 
torily or with great difficulty. Ehrlich’s haematoxylin 
did not act well: the blue coloration could not be 
obtained. Heidenhain’s iron haematoxylin stained the 
sarcomatous cells deeply, and when they were differen- 
tiated sufficiently the adjacent connective tissues had 
entirely lost the stain. It was found that Mann’s methyl- 
blue-eosin gave, on the whole, the best results, and all 
sections made were stained in this fluid. 
Sections were cut from the fully-developed tissue, and 
from its growing edge. The part of the tumour fixed at 
Port Erin included only the developed tissue and the part 
of the growing edge examined was taken from the fish 
after it had been preserved in formalin. Curiously 
enough, the fixation in the latter case was not inferior to 
that of the tissue fixed when the fish was fresh. Fig. 1, 
Pl. V represents a part of the fully-formed growth 
stained with methyl-blue-eosin, but not decolourised in 
any way. Such sections allow us to see very little of the 
minute structure of the tissue, because of the enormous 
