406 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
This species was Ditrema jaclcsoni. Agassiz adds a note as follows : 
It will be a matter of deep interest to trace the early stages of growth of these fishes, to examine 
the structure of the ovary and the eggs before fecundation takes place, etc. 
This was, however, not done in the forty years after the above was written. 
Prof. Agassiz described the structure of the ovary as follows : 
It consists of a large bag. * * * Upon the surface of it large vascular ramifications are seen, 
and it is subdivided internally into a number of distinct pouches, opening by wide slits into the lower 
part of the sack. This sack seems to be nothing but the widened lower end of the ovary, and the 
pouches within it to be formed by the folds of the ovary itself. In each of these pouches a young is 
wrapped up as in a sheet and all are packed in the most economical manner as far as saving space is 
concerned, some having their head turned forwards and others backwards. This is therefore a 
normal ovarian gestation. 
He further gives the relative sizes of adult and young. 
Dr. Webb’s account as given by Girard is as follows: 
On May 3 (1852), during boisterous and cold weather, Capt. Ottringer caused his seine to be 
drawn across the harbor (San Diego). Caught many tiger and shovel-nose sharks, two flounders, 
two specimens of a fish somewhat like our sculpin, also a number of small fish about 3 or 4 inches 
long, each of which contained ten or twelve living young. 
Girard (1858, p. 165) adds the following to Webb’s account: 
Eggs are formed within the texture of the ovarian membranes themselves. * * * The sheath 
(ovarian walls) and the ovaries are gradually increasing in bulk, as the eggs themselves first increase 
in size and the embryos afterwards. The sheath is chiefly a muscular membrane, whilst the ovaries 
are altogether vascular. 
When mature, the eggs either fall into the space between the membrane or ovarian pouches, or 
else remain attached to the ovaries until the embryos issue out of them. We are inclined to think 
that they drop into the pouches as eggs. At any rate we found very young embryos loosely con- 
tained in the ovarian pouches, when no trace of the egg membrane could be seen within the tissues of 
the ovaries. 
After leaving the eggshell they have an abdominal bag containing the remaining yolk, * which 
is gradually absorbed during a period’when neither the mouth nor the oesophagus are formed. * * * 
The soft and articulated portions of the dorsal and anal fins next assume a development reaching 
extraordinary proportions, which they again gradually lose as soon as free from parental sheltering. 
Under tbe bead of Embiotica jaclcsoni he states: 
To the upper roof of the sheath are firmly attached some highly vascular membranes hanging 
downwards and dividing the whole tube into elongated pouches or compartments. Five of these 
vascular membranes were found to be present, and by an attentive examination it was soon discovered 
that they were in fact the true ovaries, two in number, as required by the law of symmetry. 
Mr. Lord (1866, pp. 106-114, 116-119) gives tbe following account of bis discovery 
and observations:! 
At San Francisco, as early as April, I saw large numbers of viviparous fish in the market for 
sale; but then it is an open question whether these fish really arrive at an earlier period of the year 
in the Bay of San Francisco than at Vancouver Island. I think not. That they are taken earlier in 
the year is simply due to the fact that the fishermen at San Francisco have better nets and fish in 
deeper water than the Indians, and consequently take the fish .earlier. The habit of the fish is 
clearly to come into shallow water when the period arrives for producing its live young; and from 
the fact that some of these fish are occasionally taken at all periods of the year, I am induced to 
believe that they do not in reality migrate, but only retire into deeper water along the coast, there to 
remain during the winter months, reappearing in the shallow bays and estuaries in June and July, 
or perhaps earlier, for reproductive purposes ; here they remain until September, and then entirely 
disappear. 
* Prof. Eyder has already shown that this observation is erroneous, 
t For this account I am indebted to Dr. Theodore Gill. 
