60 BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Surinam toad. Only one other female fish shares with this one the dis- 
tinction just noted, namely Solenostoma , an Indian lophobranch, ir 
which the ventral fins, which are free in the male, coalesce to form with 
the integuments a pouch for the reception and hatching of the eggs. 
The entire group of the sharks and rays ( Elasmobranchii ), again, is char- 
acterized by the peculiar condition of their eggs, which are distinguished 
not only by their great size, but also by the fact that they are either de- 
posited in horny capsules, or retained in the oviduct until hatched. 
The former takes place in the common rays, certain dogfishes ( Scyllium ), 
and sharks ( Cestracion ), and in the curious CMmcera and Callorhynchus ; 
while the latter (that is, the production of living young) occurs in the 
rest of the sharks and in the torpedoes. 
As already indicated, the prevalent notion among the older natural- 
ists was that fishes of all kinds deposited their eggs on the bottom of 
the sea, and that extensive migrations were made for this purpose, 
the general impression being that the majority proceeded shorewards 
to deposit their eggs in the shallow water. This impression was prob- 
ably due to the fact that the salmon, and perhaps the herring, followed 
this habit, the former proceeding up rivers and the latter selecting cer- 
tain banks, often near land, covered with sea- weeds and zoophytes, or 
a bottom composed of stones and gravel ; and it was assumed by the 
older observers that all marine fishes followed similar habits. Thus it 
was supposed that the cod, haddock, whiting, ling, hake, and other 
fishes frequented certain banks for the purpose of depositing their eggs, 
and that various flat-fishes, such as the larger turbots and soles, came 
from deep water to shallow water for the same end. Such conjectures, 
however, were found to deviate very considerably from the facts. 
Among the earliest to notice that the eggs of certain marine fishes 
floated were the cod fishermen of the Lofoden Islands, off the coast of 
Norway. These Norwegians had noticed that what they called the 
a roe 77 of the codfish floated in the water on the great fishing-banks, 
and often at certain seasons to such an extent as to make the water 
thick. Prof. G. O. Sars, inspector of fisheries in Norway, to whom this 
remark was made, supposed that the fishermen had mistaken some of 
the lower marine animals for the eggs of fishes ; for such a feature was 
in direct opposition to anything he knew of the spawning of fishes. 
The subject, however, was soon set at rest, for he proceeded in 1864 to 
the fishing-grounds off the Lofoden Islands, and captured in the tow- 
net immense numbers of the eggs of the cod floating at the surface of 
the sea. Next year, indeed, on a calm day, Professor Sars found the 
sea covered with a dense layer of floating spawn, so that with a suffi- 
ciently large net, he could have taken tons of it. This occurred over a 
celebrated fishing-ground, on which the cod were present in enormous 
numbers, so as to form what the fishermen called a “ fish mountain. 77 
Professor Sars also found that the ova of the haddock floated, and 
among the eggs procured from the surface of the sea were some from 
