VIVIPAROUS FISHES OF THE PACIFIC COAST. 
411 
Prof. Ryder (1885) discovered that what had been taken for a yolk bag by Girard 
was a projection of the abdominal profile, caused by the hypertrophied hind gut, and 
that the inner lumen of the hind gut is filled with “villi of the most extraordinary 
length. * * If extended, some of these villi would more than reach across the lumen 
of the intestines.” Since no such structure is found in the adult he thinks it “obvious 
that this hypertrophy of the hind-gut and remarkable development of elongated villi 
in the embryos of the surf perches has some important function to subserve during 
foetal life.” This function he considers to be the digestion of the fluids secreted by 
the walls of the “ovarian sack.” 
Ryder studied material collected by Rosa Smith at San Diego, and from the date at 
which this material was taken he concludes “that during the months of October and 
November one would probably find the earlier stages, which are so desirable to clear up 
what must evidently be a most interesting chapter in vertebrate embryology.” He 
redescribes the highly vascular larval fins, and adds that all of the vascular digitations 
at the edges of the vertical fins receive their blood supply from the median aortic 
trunk, which reaches them through trunks given off from the aorta at irregular inter- 
vals of one, two, or even six muscular segments. At the base of the fins they subdi- 
vide into from two to six branches, which pass up a little to one edge of the iuterradial 
space, giving off smaller trunks to the highly vascular interradial membrane and end- 
ing in a flat sieve-like capillary mesh. The vascular trunks do not correspond to the 
number of rays, a fact which indicates “that this singular vascular supply of the ver- 
tical fins of embiotocoid embryos has attained great specialization and must be of very 
great physiological importance.” 
He further describes the peculiar vascular supply of the caudal and of the skin. 
He finds that nothing is found in the adult which corresponds to this larval condition. 
All this arrangement he considers to be for the purpose of respiration and not for the 
purpose of absorbing nutriment from the ovarian space, as Dr. Blake supposed. 
As will be seen later, I consider that both these functions are in part subserved 
by this highly specialized vascular system. 
I have published several notes on the eggs and development of the Embiotocidce , 
but since these observations will be extended and corrected in the following pages, it 
is not necessary to mention them further here. 
