VIVIPAROUS FISHES OF THE PACIFIC COAST. 
419 
the three sheets of each side have become united. The inner layers of these sheets 
sometimes form a solid tissue, but frequently they are well separated or connected by 
occasional libers only. The latter is probably an artificial condition. 
The blood vessels found in the sheets lie between the two inner layers of cells 
and are surrounded by tissues derived exclusively from the ovarian walls. They are 
always quite distinct from the surrounding tissues. 
At a glance the conditions appear quite different from those obtaining ordinarily 
in fishes, but a closer inspection shows the chief difference to lie in the nonformation 
of numerous eggs and of a large amount of yolk. If the oviferous sheets of Perea , 
for instance, should be deprived of all but a few eggs they would be similar to those 
in Cymatogaster. The difference between them would lie in the size of the cells. The 
minute structure of the ovary will be more fully dealt with in a later part of this 
work, when the growth of the ovarian eggs is considered. 
The blood supply* is derived from two vessels entering the two horns of the 
ovary. These are divided up in the front end of the ovary and traverse the ovarian 
sheets like the rays of a fan. 
Secondary sexual characters in Cymatogaster . — 1. The male is much smaller than the 
female; the latter reaches a length of about 160mm., while 120mm. is the length of 
the longest male recorded (figs. 180a, b). 
2. The anal fin of the female is normal. In the male there is a slight depression 
on either side at the base of the anterior anal rays and the rays themselves are provided 
with a gland-like structure with a free duct pointing forward (fig. 108 b). 
3. The median region of the belly in the male is naked. The anus (which is 
reached by the tips of the ventrals) is succeeded by a broad, low, blunt papilla, behind 
which lies a deep pit. In the female the papilla gives place to a circular opening of 
the oviduct. 
4. The male is much darker than the female. Each row of scales is provided 
with series of pigment spots which form lateral bands. Dorsally the pigment spots 
sometimes become so numerous as to give the fish a black appearance. There is also 
a conspicuous black spot on the preorbital. 
In the female the ventral regions, belly, and breast are free from pigment and the 
cheeks and lower parts of the head are also but sparingly pigmented. The lateral 
bands of dark are quite inconspicuous except in three vertical bars on the sides of 
the abdomen. In other regions they are overlaid by a golden tinge. The preorbital 
spot is either absent or inconspicuous. 
Copulation . — The act of copulation has never been observed in the Embiotocidce. 
Blake suggested that the ventral surfaces are appressed, the heads of the fish point- 
ing in opposite directions. Ford supposes that “fecundation is accomplished through 
the medium of the sea water.” It has lately been shown that contacts of the genital 
openings is not necessary for the transference of spermatozoa to the cloaca of Die- 
myctelus. The same may be true for Cymatogaster. 
* In Amphistichus the ovarian sheets are not united below, but hang free, and the blood supply, 
instead of being derived from vessels radiating from the anterior end, are derived from a vessel running 
along the dorsal part of the ovary. 
