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MUSEUM OF COMPARATIVE ZOOLOGY. 5 
when they reached me, and only one was in perfect health. This one 
was kept in an aquarium of about four gallons of water until February 
10, 1892. I can fully confirm the statements of other writers concerning 
the extreme tenacity of life exhibited by these fishes. During the last 
two months that this specimen was kept, the water was not changed nor 
aerated in any way, nor was food given to the fish ; and I may say that 
it did not, so far as I could determine, take food at all during the time 
of its confinement, except the small quantity naturally contained in the 
water. Worms were placed in the aquarium, but had to be removed, 
untouched so far as I could see, to prevent contamination of the water 
by decomposition. When the fish was killed, it was to all appearance 
as well and as lively as it had been at any time during its captivity. 
Experiments for the purpose of determining whether the eyes in this 
individual still performed their proper function were not very satisfac- 
tory. Very frequently when the water was suddenly illuminated by 
a strong light thrown into the aquarium, standing in a dark room, the 
fish was found to be moving about at the bottom with considerably more 
than its wonted activity. This activity would continue for only a short 
time, when the fish would either move more slowly or would settle down 
and become quite still. As the movements were almost always rather 
slow and infrequent when the fish could be seen, I am inclined to in- 
terpret this behavior as indicating that the fish was sensitive to the light. 
However, repeated attempts to produce conditions that would cause it to 
choose between light and darkness, if it had the power of such choice, 
were without positive results. On the whole, both from these observa- 
tions on the living fish, and from the structural conditions to be here- 
after described, I am of the opinion that the power of perceiving light 
is not wholly lost, even in the adult. The specimen kept alive was 
32 mm. long, or about 20 mm. shorter than the largest ones that I have 
seen. 
The pink color mentioned by all those who have written of this fish is 
a quite striking feature in its general appearance. It is not at all due 
to pigment in the integument, but to the extreme richness of blood- 
vessels situated in the sub-epidermal connective tissue, as will be shown 
later. It disappears entirely in preserved specimens, the color becoming 
a dull opaque white, particularly in large individuals. In small individ- 
uals, however, the color of the dorsal side of the head and body is quite 
dark from the presence of brown pigment. The causes to which these 
different colors, under different conditions of development and treatment, 
are due, are of considerable significance, and I shall speak of them more 
