No. 465.] STUDIES OF MYXINOIDS. 627 
not more than six or eight of the total number died a natural 
death. Of these two hundred and fifty, about seventy-five were 
kept in the aquarium from six weeks to two months or more 
before I killed them, and more than a hundred were kept for 
a month before being killed. 
GENERAL DESCRIPTION. 
It is not necessary to describe the general appearance or 
characteristics of Bdellostoma, as that has already been admir- 
ably done (Ayers, '94) ; but one or two poihts of interest were 
ascertained in reference to their size. Of 550 specimens 
measured, the longest was 24.5 inches, while 104 measured 20 
inches or over, and 64 were between 19 and 20 inches long. 
When it is remembered that of these 550 specimens, between 
350 and 400 were caught in traps that did not favor the ingress 
of the larger hagfish, the average length will be seen to fall in 
the neighborhood of 19 to 20 inches. In regard to their length 
at hatching, the smallest free-swimming hagfish that fell into 
my hands measured scant two and three eighths inches (60 
mm.), while a few days later I took an embryo from the shell 
that measured a trifle more than two inches and a half (65 
mm.). This embryo was apparently ready to hatch, as it swam 
vigorously as soon as it was freed from the shell. 
These newly hatched hagfish have the same shape as the 
adult, the only perceptible difference between them and their 
elders being that their tentacles are relatively a little longer 
than those of the mature fish. At the time of hatching, the 
head is an eighth of an inch in diameter; when from twelve to 
fourteen inches long the proportions of head to body are some- 
what different, the head measuring from three eighths to one 
half inch across, and thus being relatively thinner. When 
about fifteen inches long, however, the hagfish begin to increase 
' rapidly in girth, measuring at least three fourths of an inch across 
the head, while the larger ones measure still more. This 
marked change of form does not, however, as might be thought, 
mark the time of sexual maturity, for an individual only twelve 
inches long and slim in proportion was found to have a well 
