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Part III. — Ninth Annual Report 
enlargement is not confined to pelagic forms. It does not occur in the 
ova of the trout, lumpsncker, herring, or smelt (which are rapidl}^ deposited), 
but it occurs markedly in other forms, such as Liparis, Cottus huhalis 
(probably also Cottus scorpius), Syngnathus acus, Anarrhichas and, as 1 
am informed by Sir James Maitland, Bart., it occurs also in the grayling. 
The process is probably essentially similar both in pelagic and such 
demersal ova. The degree of increase in bulk varies in different species, 
and is in many cases indicated below. In some fish the increase is not 
great ; in the plaice it is very marked, the ovum suddenly attaining four 
times the bulk, as it is also in Anarrhichas. In the long rough dab 
the expansion appears to take place just prior to extrusion, and the fully- 
mature ovum is very large. 
2. Proportional Number of Ova Produced by Different Species. 
As shown in detail below, the number of eggs produced in each season 
by different species of sea fish varies enormously — from the 20,000,000 
or 30,000,000 of the ling to the few hundreds of the pipefish. As a rule, 
the larger the species the greater the number of ova produced, but this is 
subject to many exceptions. For example, the halibut produces far fewer 
eggs than the ling, cod, or turbot ; the flounder far more than the lump- 
sucker. The flounder, in proportion to its size, is the most fecund of all 
seatish, and the lumpsucker the least so. The ratio of the number of eggs 
to each 1000 grains of the rest of the body was determined, and a few of 
the results may be given. The flounder produces from 120,000 to 
198,000 ova for each 1000 grains of the rest of the body; the cod from 
30,000 to 60,000; the haddock from 13,000 to 32,000; the long rough 
dab from 35,000 to 81,000 ; the plaice from 9,000 to 20,000 ; the lump- 
sucker from 1,300 to 2,800; the sparling from 40,000 to 45,000 ; the 
herring from 4,300 to 9,000. 
As a rule, also, the larger the individual fish of the same species, the 
greater the number of ova ; but this statement is likewise subject to 
important exceptions. 
The enormous fecundity of most marine food-fishes is a measure of the 
destruction that takes place among the eggs after they are shed, and 
amongst the young fish ; and the rational principle of the artificial pro- 
pagation and culture of sea fish is based upon careful protection at these 
stages. 
3. Variation in Fecundity in Individuals of the same Species. 
In the course of the investigation it was rendered very evident that 
wide difference exist among individuals of the same species, in regard 
to the proportional weight of the ovaries, the number of ova produced, 
&c. Some of these are indicated below. In order to obtain more certaiu 
data on this subject sixteen herrings were carefully examined, this species 
being selected because ripe specimens were easily procured, and the ova 
were large, uniform, and not very numerous. Most of the details are 
given on p. 260. The number of ova produced varied from 21,500 to 
47,466, the mean being 31,768. The ratio of the weight of the ova to 
the rest of the body at 1,000 ranged from 152*39 to 345-16, the mean 
ratio being 242*3. The ratio of the number of ova to each 1,000 grains 
of body-weight varied from 9,695 to 21,431, the mean being 14,392. 
The number of eggs per grain varied from 43*19 to 91*83, the mean being 
61-24. 
From these and other data it appears that the reproductive organs and 
the reproductive function are extremely variable among different indi- 
viduals of the same species of fishes. 
