436 THE ZOOLOGIST. 
size of the ova is not invariably the same in individuals of what- 
ever size, but, as far as our experience reaches, is even often 
characteristic of the species of a genus.’ Dr.John Davy, in 
1852, published the result of his accurate investigations upon 
this point, for which purpose he selected the Charr. He says of 
the ova:—“ Those I have examined I have found to vary in 
diameter from 0°16 to 0°18 and 0°20 of an inch, and in weight 
(after removal of the adhering moisture by wiping), from 0°7 to 
1 grain each.” I have personally measured the size of fourteen 
ova taken from a single example of an Indian siluroid (Osteo- 
geneiosus); they were 0°4 to 0°5 of an inch in diameter, thus 
showing variations in the size of the ova from a single fish results 
confirming the investigations of Davy in a Charr. If the size 
can thus vary in the eggs from one specimen, it does not seem 
remarkable that it may do so more widely in nearly related 
genera; thus, the Smelt (Osmerus), belonging to the Salmon 
family, has by no means large ova, for in two examples, each 
weighing two ounces, there were found in one 38,278 eggs, and in 
the other 36,652 eggs. Davy counted 1230 ova in a Charr, while 
in the Salmon and Trout it has been observed that they carry 
somewhere about 1000 eggs to each pound of weight. Such a 
proportion, however, does not apply to those which are less than 
one pound, and even in larger fish it is subject to considerable 
variation. In fishes that spawn at least twice a year, and like- 
wise protect their young, the number of eggs is less than what 
generally obtains in other genera. Thus in a Walking-fish 
(Ophiocephalus) I found 4700. 
As to the colour of fish-eggs, they are very various; in some 
fresh-water siluroids they are of a light pea-green, as I have 
observed in the Indian Scorpion-fish, and as also occurs in Silwrus 
glanis, while in the Salmon and Trout, and Grayling, they may 
be coral-red, yellow, or pure white. As to the places where fish 
deposit their eggs, these are exceedingly various, as might be 
anticipated, because some sink in the water while others float. 
Professor Sars found the ova of several of our best-known fishes 
floating on the surface of the sea, where they remain during the 
whole period of their development ; among such as he was able to 
hatch out were those of the Cod, Haddock, Mackarel, Plaice, 
Gar-fish, and a Gurnard. This fact is interesting because it 
TT 
2. a | 
shows that trawl-nets could not occasion injury to these eggs, — 
