PREFACE ; vil 
SESSIONAL PAPER No. 38a 
2. Dratoms AND LopsterR Reartnc.—(Professor MacClement.) 
Professor Knight’s laborious researches have shown that efforts to rear lobsters 
through the young stages in hatching ponds have been hampered by several difficulties, 
one of the most serious being the diatom pest. After hatching, larval lobsters crowd 
near the lighted surface layers of the water, until after four or five moults they seek 
shelter at the bottom. While under the influence of sunlight they become loaded with 
- microscopic plants, the diatoms forming a feathery coat as it were, and so incom- 
mode the floating larval lobsters that they were observed to sink to the bottom of the 
boxes used in the experiments at Long Beach, Nova Scotia. 
After a description of the structure of diatoms, and of the three or four species 
chiefly affecting young lobsters, the author dwells upon the two principal methods of 
combatting the pest, viz., by copper sulphate solution, which proved fatal when only 
14 to 2 parts in three million parts of water were tried; and a second method, i.e., the 
screening from direct sunlight of the rearing boxes. Under this latter method larval 
lebsters loaded with diatoms soon lost a great many of them, and they moulted earlier, 
viz., in nine days, whereas the lobster fry not shaded from sunlight did not moult 
until the thirteenth day. Licmophora was the chief pest, but a list of nineteen species 
of diatoms occurring in the boxes is given, and the relation of the plankton to the 
sessile diatom pest is interestingly explained. 
3. THE SCALES OF THE SPRING SALMON.—(Dr. C. McLean Fraser.) 
After reference to other work on fish scales, as affording information on the 
growth of fishes, Dr. Fraser states that the rings of growth in the Spring Salmon or 
Quinnat are much more regular in arrangement than those of the herring scale, and 
closely resemble the growth in a twig of wood (in cross section); the rings being 
closer and more compact in winter (the “winter check”), whereas from late in April 
to late in November the rings are wider, like the looser texture of the summer growth 
in the twig. Dr. Fraser noticed between March 17th and April 22nd, and between 
November 27th and January 5th, there were in many specimens evidences of retard- 
ation of growth, as Einar Lea had also noticed in the Norwegian herring. Careful 
tests made by the author did not show any relation between the temperature of the 
water and the retardation or the acceleration of growth, and the “graphs” given in 
the paper fully confirm this negative result. Nor does variation in food-supply appear 
to explain the phenomenon. An exhaustive study of the growth of the fish was made 
from the time when the fry (14 inches long), not yet provided with scales, descends 
to the sea. 
At the end of the year the fish are 10 inches long usually and weigh about half a 
pound. Not all the fry descend the first year; but some remain, and acquire their 
scaly covering in fresh water. The summer rings are close together, so slow is the 
growth of the fish in fresh water, and the two types of fish are remarkably contrasted 
even when both mingle in the same schools in the sea. Thus, the fish which reach the 
sea from March to April in their first year, may be 203 inches long and weigh 4 pounds 
or over; but the delayed fish are only 14 inches and of a weight of a pound. In the 
third year they are respectively 284 inches and 14 pounds weight, and 23 inches and 
6 pounds weight; while, in the fourth year, they are in length 33 inches and 30 inches, 
and in weight 22 pounds and 16 pounds respectively. The more rapid growth of the 
“sea type” indicates that the retention of the fry in ponds is a mistake, and based on 
lack of accurate knowledge of the peculiarities of the Pacific Quinnat Salmon. Four 
very graphic plates and two diagrams establish the important conclusions reached 
by Dr. Fraser. 
