282 
NATURE 
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[Fuly 23, 1885 
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suitable hatching-tanks and at least one large sea-water pond ; 
(2) a cruiser adapted for carrying on dredging and other opera- 
tions ; (3) two small steam tenders adapted for inshore work ; 
(4) a sufficient annual sum of money to meet the working ex- 
penses of hatching and other operations and to provide the neces- 
sary apparatus, From information gained in America the Board 
feels that, if provided with sufficient funds and with increased 
powers, it might be able greatly to increase the number of useful 
food fishes in the firths, bays, and other waters around the coast. 
The marine station at St. Andrews is now in working order and 
an assistant naturalist has been sent to carry on investigations 
under the direction of Prof. McIntosh, F.R.S. A number of 
interesting inquiries have been instituted, especially on the nature 
of the eggs and rate of growth of fishes and the life-history of the 
common mussel. The Scientific Committee, who felt the assist- 
ance of an experienced naturalist devoting his whole time to the 
work of inquiry to be not merely expedient but necessary, have 
been so fortunate as to secure the services of Mr. Brook, F.L.S., 
of Huddersfield, who had been studying for some time the history 
and habits of fish, and gained considerable experience in organ- 
ising and carrying on a marine laboratory. A temporary la- 
boratory has been erected at East Tarbert, a convenient situation 
for studying the west coast fishing and from which it is possible 
to study not only the herring-fishing in Loch Fyne, but, with a 
good steamboat, to embrace the whole area of the Firth of 
Clyde. Mr. Brook is engaged in studying the development of 
the herring, and the result of his experiments will be described 
in detail in papers the first of which is now appended— 
the others to be presented to the Board in the autumn. 
Mr. Brook has also in hand a paper on the ‘‘ Food of the 
Herring,” to be completed in the autumn. The Directors of 
the Rothesay Aquarium have very kindly placed the tanks of 
their institution at the service of the Board, and this will be of 
great assistance in the study of the life-history of various food 
fishes, especially during the winter months. There is now at 
the service of the Board a small laboratory in the Cromarty 
Firth, and it is hoped that a marine laboratory may soon be 
established near the mouth of the Firth of Forth. 
The most important paper in the scientific appendices contains 
“¢ Observations on the Spawning of the Cod,” by Prof. Cossar 
Ewart and Mr. George Brook. The authors say that it is now 
twenty years since G. O. Sars discovered, what our fishermen 
still decline to believe, that the eggs of the cod float on the 
surface of the sea, and only sink when dead.  Sars’s after- 
investigations showed that the eggs and the milt are of less 
specific gravity than the sea water, and consequently float, also 
that the micropyle lies near the lower portion of the egg. The 
experiments reported were carried on in Rothesay Aquarium on 
fish which had been in the tanks for four years. In February 
several cod appeared to be reaching maturity; early in 
March the fish refused food, and a few days afterwards 
eggs in an early stage of development were floating on the 
surface of the water, so abundantly that hundreds were collected 
in a few minutes by means of a piece of muslin placed over the 
overflow of the tanks. The temperature of the water was 
43° F., and the specific gravity a little over 1°024. The eggs 
were usually found during the first few days in from the 2- to 8-cell 
stage at 8 a.m., so that they were most probably shed about 
daybreak. Later batches shed between 6 and 7.30 p.m. were 
found at the latter hour with the disk already forming. The 
great transparency of the living eggs makes it almost impossible 
to notice them as they rise through the water, whilst the dead 
eggs, being slightly opaque, are easily recognised as they are 
carried to and fro by the currents. For some time before the 
first eggs reach maturity, and during the early part of the spawn- 
ing period, the fish not only refuse food, but give up their regu- 
lar movements around the tank and swim about in small groups 
or rest together at the bottom, swimming and resting alternately. 
Sometimes a single female would swim leisurely about for a few 
minutes attended by a single male, and often settle down in a 
corner of the tank and rest till disturbed by her attendant. 
The activity of the males was specially evident at dusk and in 
the early morning, and it was apparently during these periods of 
activity that the eggs were shed and fertilised. One day, for 
example, there were no eggs visible on the surface of the water 
at 6 p.m., while a considerable number were obtained at 7.30, 
which, as the germinal disk was not completely formed, had 
in all probability been quite recently shed while the fish had 
been swimming about the tank in groups, From the 
observations made, it seems, as suggested by Sars, that 
the eggs and milt 
freely about in the 
among the females, 
fertilising the water 
are shed while the fish are swimming 
water. The males swim indiscriminately 
sometimes over, sometimes under them, 
through which the shed eggs are slowly 
rising to the surface. Eggs were pressed from a ripe female 
and fertilised artificially. They developed normally, but it was 
found that a few kept for some hours in a small glass cell in a 
warm room, for observation under the microscope, began to 
show similar abnormalities to those figured by Ryder (‘‘ Em- 
bryology of Osseous Fishes,” Report U.S. Fish Commission, 
1882). Too high a temperature has a similar effect on other 
eggs, but those which float on the surface are naturally more 
sensitive. The females, like the Salmonidz, are capable of 
withholding the flow of ripe eggs toa certain extent. A limited 
number only are ripe at one time, and if the unripe be forced 
out they sink to the bottom and are incapable of being fertilised. 
The ripe unfertilised egg has a milky appearance and is more- 
over not so transparent as the fertilised one, so that by a little 
practice the two can be distinguished without the aid of a micro- 
scope. As soon as an egg begins to die or to develop abnorm- 
ally, the milkiness returns and it sinks to the bottom. Whether 
fertilised or not, the eggs float immediately after extrusion, but 
in the latter case they die and sink to the bottom in twelve to 
fourteen hours. During this time no change was observed to 
take place in the unfertilised egg, the small oil-vesicles around the 
yolk remaining constantly in their primitive condition. In per- 
fectly still water (sp. 1°024) the eggs float in a dense mass ; when 
carried along by a strong current they become suspended at 
various depths, but none that are living lie at the bottom. At 
any rate all found there were either dead or dying. It seems 
that large numbers of the pelagic fish eggs have been dredged at 
the Fishery Board Station at Tarbet. With the sea perfectly calm, 
most eggs were obtained on the surface ; with a slight ripple the 
net had to be kept just under the surface and in other states of 
the weather to be lowered two or three feet under the surface. 
The eggs having a specific gravity only slightly less than that of 
water, do not rise to the surface very rapidly. In one case 
noted it took an egg four minutes to rise through 1} inches of 
water. The milt also has less specific gravity than sea-water, 
and rises to the surface when shed. If forced down, it 
gradually rises again, disseminating as it does so. During 
the spawning process the water in the tank became slightly 
clouded by the spermatazoa, which were spread through 
it. The milt is, however, shed in such a thin stream 
under natural conditions that it is difficult to detect it. The 
eggs are capable of being fertilised a considerable time after the 
fish is dead, and also some time after they have been shed. Light 
appears to have considerable influence on the spawning process, 
and under natural conditions the eggs seem to be shed at day- 
break or dusk, when the light is not strong. The observations 
made justify the conclusion that the spawn is shed while the 
fishes are swimming about freely in the water, and that the eggs 
are fertilised at, or as they rise to the surface, this being facili- 
tated by the position of the micropyle, which is always found in 
the lower hemisphere of pelagic fish ova. To show the facility 
with which some fish ova are fertilised, an experiment on herring 
ova may be here mentioned. Three batches of ova secured from 
a living female were placed in tumblers, and water added from 
an adjoining tank. It was intended to fertilise each batch 
separately, and at fixed intervals, but it was found that though 
no milt had been intentionally added to the second or third 
tumblers, the water not being from the tank in which the herring 
were kept, spermatozoa must have been introduced with the 
water, as the second and third batch of eggs developed exactly 
like the first, and were ultimately hatched out. As Kupfer 
points out, it is necessary, in order to keep eggs unfertilised, to 
get a fresh supply of water direct from the sea. 
Mr. Brook’s first paper on the ‘‘ Development of the Herring ” 
gives a résumé of what is already known on the subject, as pre- 
liminary to the result of his own investigations. He also sends 
notes of rare and curious fishes sent to the Board. Dr, M‘Intosh 
details the work done by himself and by his scientific visitors to 
the St. Andrew’s Laboratory. Prof. Cossar Ewart reports on 
the progress of Fish-culture in America, and Mr. Young on the 
Northern and Western Salmon Rivers. The Report is both 
interesting and encouraging. It is difficult to form an adequate 
idea of the immense importance of their sea-fisheries to the 
people of Scotland. But it may be stated that about half a 
million of people, or about one-seventh of the entire population 
of Scotland, are connected with this industry, and more or less 
