58 BULLETIN OF THE UNITED STATES FISH COMMISSION. 
the spawn was thrown into the water from the salmon caught by fisher- 
men and sold to the canneries. As to catfish, I believe their importa- 
tion to this coast was an error ; and the board of fish commissioners who 
authorized their importation, if I remember rightly, came to the same 
conclusion. The fish which they destroy, however, are perch and dace ! 
and their spawn, which at one time were found in vast numbers in the 
Sacramento. 
San Francisco, Cal., June 8, 1887. 
18.— THE EGGS OF FISHES.* 
By Prof. McINTOSH, ll. i>., f. r. s. 
[Abstract of an introductory lecture delivered to the class of natural bistory in the 
University of St. Andrew’s.] 
It is but a short time since works devoted to the history of British 
fishes were devoid of allusion to any other mode of spawning than that 
by which the eggs of our marine fishes are deposited on the bottom of 
the sea. Indeed it was believed by most naturalists that the latter was 
the normal mode of deposition. As a consequence, some of the text- 
books at present in use either follow the latter view, or do not specially 
allude to the question. 
The eggs of all fishes are produced in the ovaries, which are symmet- 
rical organs lying beneath the vertebral column, and which at different 
periods of the year present various appearances according to the degree 
of development of the eggs. Thus in the quiescent condition of the 
organs their size is insignificant, while the fully developed ovaries of 
the codfish occupy a large space and weigh several pounds. At first 
the eggs are very small, but they gradually increase in size by imbibing 
nourishment from the ovarian follicles in which they are placed. 
A feature not sufficiently insisted on in Great Britain is the fact that 
only a portion of the ovary in most marine fishes becomes u ripe ” at a 
given time. This provision appears to be admirably suited for the in- 
crease of the fishes, a constant succession of the embryos being thus 
liberated, and time afforded for those of one stage to disappear from the 
surface of the ocean before those of the succeeding take their places. 
In America this condition has been clearly described in the report on 
the cod fisheries of Cape Ann,* by Mr. R. E. Earll; but the account does 
not seem to have come under the notice of Mr. William Oldham Cham- 
bers, who alluded to the subject a year or two afterwards.! 
Mr. Earll observes that u the individuals [that is, the cod] do not de- 
posit all their eggs in a single day or week, but probably continue the 
* See U. S. Fish Commission Report for 1878, pp. 685, 714, et seq. 
t “Fish and Fisheries,” prize essays, International Fisheries Exhibition, Edinburgh, 
1883, p. 187. 
