360 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
or spermatozoan ; and while this is generally attributed to injuries received in capture, 
attention may be directed to the suggestion that the periods of scarcity may be in part 
due to lowered vitality and fertility of the fish. In this case it is obvious that to 
attempt artificial propagation while the condition lasts would be a waste of time. 
But this explanation probably fails to reach the root of the matter, as a study of 
the spermatozoa and eggs before and immediately after fertilization indicates, by the 
activity of the former and the response of the latter, a good vital condition. Fertiliza- 
tion is very easily accomplished, and the rhythm of development is strikingly constant 
and simultaneous in all of the eggs of a batch. The unfavorable condition must be 
sought in the method of propagation, and many facts point to the conclusion that the 
shore waters utilized for the purpose lack the physical qualities, and the apparatus fails 
to supply certain important conditions requisite to the healthy development of the eggs. 
To this conclusion are opposed the results reported from Gloucester Station, and these, 
together with the partial success of experiments with water of increased density, lead 
to the hope that the mackerel may some day be successfully hatched. 
There is, however, a further serious practical difficulty to be encountered. Even 
were artificial propagation as successfully accomplished with the mackerel as with 
the cod, and 50 per cent of the eggs handled turned out as fry, could the demands 
imposed by the figures given above be met 1 ? During the season of 1890 the collection 
of mackerel eggs was pushed with great vigor by the United States Fish Commission, 
with the result that about 23,000,000 eggs were taken, a number which, even if all 
were hatched and deposited under the most favorable conditions, would fall many 
times short of producing 21,000,000 fish three years later. In 1897 less than 4, (*00,000 
were obtained, although every effort was made to conduct operations on a large scale. 
These difficulties have led to the proposal that suitable arrangements be made 
with the captains and owners of seining vessels by which one or more spawn takers 
(probably members of the crew would serve) would accompany each vessel during 
the spawning season. Upon the capture of a spawning school vast numbers of eggs 
could be taken, immediately fertilized, and turned overboard under the best natural 
conditions for further development. 
The method has several obvious advantages — (1) great numbers of eggs which 
would otherwise be destroyed would be started on the way to future usefulness; (2) 
it could be applied at small cost, and (3) in one respect it would be a gain over the 
natural deposition of eggs, in that more certain fertilization would be insured. The 
facts upon which this last statement is based are founded not upon investigations of 
the mackerel, but of the cunner, where the gain is about 30 per cent. 
One disadvantage of the method would be that the eggs would be endangered by 
contact with the waste thrown overboard during the splitting operations, and from 
predaceous fishes thereby attracted. Moreover, in view of the above figures, it seems 
futile to hope that operations could be conducted on a sufficiently large scale to be of 
any considerable benefit. If it ever becomes possible to confine the fry until they 
reach a considerable size, say until after they have assumed the adult form, then it may 
be possible to secure the supply of eggs in this way, to transport them to a station 
of great capacity and operating under conditions most favorable to the development 
of the species, such as would be obtainable upon an ocean-going steamer or an 
outlying island, and thus to bring about the desired result. But in view of the great 
area covered by the wanderings of the mackerel, of the vast numbers which inhabit 
