of the Fishery Board for Scotland, 
247 
mature, weigh 37,605 grains, or nearly 5 J lbs. Considering the need of a 
certain number or weight of ova being produced annually to be the primary 
factor, I think the above facts explain one or two phenomena hitherto 
obscure. 
First, it appears to me to explain the majority of cases in which the 
females of a species are in excess of the males. I have shown that among 
most sea fishes there is a general and sometimes a great preponderance 
of females.* Of 20 species investigated 18 produce isolated pelagic 
ova, and in at least 16 of these females are more numerous than males. 
The exceptions given are the flounder and the brill ; but only 23 of 
the latter were examined, and the deduction as to the sex-proportion 
is therefore uncertain. 217 flounders were examined, and the sex-propor- 
tion (84 females to 100 males) is probably approximately correct. It 
may possibly have relation to the exceptional fecundity of the female — the 
flounder producing a greater number of ova in proportion to its size than 
any other sea fish. On the other hand, among fish with demersal ova 
which are extruded in large quantities, the males predominate. It is 
generally held that the male salmon is more numerous than the female f ; 
of 28 lumpsuckers examined, 22 were males and 6 females ; of 59 catfish, 
33 were males and 26 females. In the angler, which, although its ova 
are pelagic, is comparable to the above fish with demersal ova, inasmuch 
as they are all shed together, of 77 specimens no less than 61 were males, 
and only 16 were females. I am not certain that among such small fish 
as Coitus, Liparis, Gasterosteiis, &c., where the ova are probably shed in 
comparatively small quantities, the males always predominate in numbers. 
From these investigations on the sex-proportions and the fecundity of 
marine fishes, it may be regarded as a general rule that, in a species 
which produces a large number of ova, and in which the females pre- 
ponderate in numbers and size, the ova are pelagic and not demersal. 
Second, I think the generally greater size of the female is explained in 
the same way. The female is larger among all flatfishes, and in the 
whiting and gurnard, but it is a little smaller in the cod (956 to 1000) 
and haddock (989 to 1000), catfish (939 to 1000), and angler (879 to 
1000). 
Third, it explains not merely the gradual growth of ova to replace the 
mature ova shed during a prolonged spawning period, but the more or 
less sudden increase of bulk which occurs in the ovum shortly prior to 
its extrusion. In almost all the ovaries examined in which ripe ova 
were present, this was a marked feature, and in a number of specimens 
the proportion or percentage of these large ova present at one time was 
determined. In the gurnard the percentage ranged from 0-9 to 2 "6, in 
the haddock from 4-6 to 37 '6, in the whiting from 17*1 to 20, in the 
saithe about 9, tusk about 1, turbot about 4 "5, in the plaice about 6, in 
the flounder 5 to about 8. The proportion of these fully mature hyaline 
ova, while it seems to vary in different species, increases with the progress 
of spawning. It seems to be due to sudden accession of fluid from the 
ovarian follicles, which increases the bulk of the ovum and renders the 
opaque contents clear by dilution. When the ova were boiled, those 
which bad suffered the hyaline enlargement were always much paler, 
watery, and more easily ruptured than those which were small and opaque 
— the latter becoming intensely white. In pelagic ova it is at this stage 
that they first acquire the property of buoyancy ; but this sudden hyaline 
* * The Proportional Numbers and Sizes of the Sexes among Sea Fishes. ' — Eighth 
Annual Report of the Fishery Board, part iii. p. 348, 1890. 
t Vide Darwin's Descent of Man, p. 249 ; Salmon Problems, by J. Willis Bund, 
1885 ; and Part II. of the present Report. 
