412 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
CYMATOGASTER AGGREGATUS Gibbons. 
Cymatogaster aggregatus is probably the most abundant species of the Embiotocidce, 
and is found along the entire western coast of the United States and part of Lower 
California. 
Breeding habits. — During the summer and fall this species is rarely seen, as it then 
probably lives a short distance off shore in deep water or among fields of Zostera. In 
November and December it approaches the shore in large numbers, and is caught 
with hook and line off the wharves in San Diego and San Francisco bays. The greater 
part of the specimens so caught are females, there being rarely a male among them. 
This is probably due in part to the facts that the male is much smaller than the female 
and, farther, that this is not the period of copulation. The largest females become 
gravid about the first of December (one very large one was found with developing eggs 
on November 1, at San Francisco) ; by the middle and latter part of the same month 
the greater number of those taken are with eggs iu various stages of development. 
During January the smaller ones caught are with developing eggs, while the smallest, 
those which do not take the hook and can only be procured with a seine, have eggs 
in similar stages during February.* The oldest are, as a rule, sexually ripe earlier in 
the season. The same variation of the time of maturation was observed in the other 
species of this family. 
Methods of studying living eggs. — The fishes were kept alive in salt water until 
needed. The spinal cord was severed and the ovary immediately excised and brought 
entire on a glass slip. The ovary was then slit open and the oviferous sheets 
unfolded. If there were free eggs they were placed together near a fragment of the 
ovary and the whole covered with a glass slip. The eggs could thus be examined in 
their natural fluid, and I have succeeded in keeping them alive for an hour. The 
oviferous sheets being very thin, a fragment of one could be spread out, covered and 
* TIME OF MATURATION AND SIZE OF EGG OF OTHER SPECIES OF EMBIOTOCID/E. 
Embiotoca jacksoni : The first one with eggs was noticed November 12 (1889). One of the eggs 
found at this time was in the two-cell stage, all were free from the follicle. The diameter of the egg 
membrane is about .7 mm., the smallest observed being .53 mm., the largest .92 mm. The diameter 
of the yolk is about .45 mm. 
Amphistichus argenteus. Diameter of the egg membrane .65 to .68 mm. ; yolk .441 to .49 mm. ; oil- 
globules .14 mm. ; green eggs near maturity .65 mm. The water space is therefore, as in Cymatogaster, 
formed by the contraction of the yolk during maturation. 
The specimens taken at San Diego, where I had au opportunity of examining large quantities, 
are of three sizes. The largest measure about 300 mm., the second in size 160 mm., and much smaller 
ones of variable sizes. There are, of course, intermediate sizes between the largest, 300 mm., and 
the second, 160 mm., but the groups are quite well marked. The largest have ripe eggs as early as 
November 12 (1889). The second in size have eggs near the middle of December. The following is 
from my notes, December 19, 1889: “A large number of individuals taken to-day, 160 mm. long; all 
have the eggs nearly equally developed. The germ is nearly at the close of segmentation; the eggs 
are still inclosed in the follicle. Only in one specimen were the eggs free. In these the gastrula 
covered the entire yolk. December 27 one female 160 mm. long was obtained; the embryo is 
hatched; the yolk is almost all absorbed. There is a continuons dorso- ventral fin-fold. These 
eggs, therefore, hatch in less than a week.” 
I did not determine the maturing period of the smallest individuals, but on December 10 I made 
the following note: “The smallest have eggs quite green.” 
On December 10 the largest contained young from 5 to 7 mm. long. The larva at the end of the 
first month would probably average 7 mm. 
