;38 



NA TURE 



IFeb. lo, 1887 



much handling, and a trained girl can give the slight 

 motion which is required to the eggs without actually 

 touching them with the feather at all. Each box is en- 

 tered by a number in a book, and a record of the number 

 of dead eggs daily taken from it is kept on a printed form, 

 and afterwards entered in the same book. Two girls only 

 are employed in attending to all the hatcheries at Howie- 

 toun. The stage in the development of the ova between 

 the formation of the blastoderm and the appearance of 

 the eyes is called the " spectacle " stage, and the health 

 of the embryo can be estimated by certain signs at this 

 period ; but the description given of these signs is not 

 easy to follow. Up to the eye stage the ova are very deli- 

 cate, but as soon as the eyes appear the eggs can be 

 handled, and this is the best age for packing for the An- 

 tipodes. Eggs for America or Europe are packed at a 

 later period, when red blood has appeared. When the 

 eggs are read)- to hatch, the gril/cs are taken out, the 

 boxes cleaned, and the eggs are emptied off the tf/vy/i'^ on 

 to the bottom of the box. The depth of water in the 

 boxes containing the alevins is only 3 inches. The alevins 

 congregate in dense masses in the corners and against the 

 sides of the hatching-box, and the motion of the pectoral 

 fins causes a continuous current to descend downwards 

 through the mass. When the yolk-sac is nearly absorbed, 

 the fry are fed with food prepared from fillet of beef or of 

 horse, and yolks of hard-boiled eggs. The food is made 

 into paste in a mortar, and rubbed through " feeding- 

 spoons " of perforated zinc into the hatching-box. 



Next follows an account of the method of despatching 

 living fry. These cannot travel for more than twenty-four 

 hours, and they are sent in tanks quite full of water, as 

 motion of the water e.xhausts the fish at this stage. The 

 greater number of the fry, after a short time in the hatch- 

 ing-house, are placed in ponds constructed of wood, 100 

 feet in length, where they remain throughout the summer, 

 and where they are fed daily by hand for the whole time. 

 It is stated that 100,000 trout eleven months old would 

 consume between two and three horses a week. 



A considerable amount of stocking is effected with 

 yearling trout, which are carried in conical tanks. 

 The fish must be starved some days before being de- 

 spatched, as, if placed in travelling-tanks when fully fed, 

 they rapidly make the water foul. In the bottom of the 

 lid of the tank is an inverted cone perforated with holes 

 and filled with ice ; this keeps a constant temperature, 

 and promotes aeration of the water. Two-year-old, and 

 even larger, trout are also sent out ; these are placed in 

 larger tanks, provided with small wheels, but constructed 

 on the same principle. 



In Chapter III. an elaborate account is given of the 

 methods of packing ova. The first operation is to trans- 

 fer the ova which are to be packed from the grilles to 

 peach netting stretched on square wooden frames. This 

 step is carried out in a specially constructed sink, through 

 which water is kept running. The ova are emptied from 

 ihtg'ri'lle into a wooden box, from which they pass into a 

 leaden basin with a narrow bottom. One of the frames 

 is then floated in the sink, and a glass measure contain- 

 ing HOC eggs is used to measure the eggs from the basin 

 on to the frame. The frames are placed in the packing- 

 room in piles, one pile for each box. Next morning the 

 frames are examined, so that any egg with an ill developed 



embryo may be picked out. Then, a scjuarc of swan's- 

 down, contained in a special tray, is placed over the eggs 

 on the frame, and, the two being suddenly reversed, the 

 eggs rest on the swan's-down without altering their relative 

 position ; thus each egg lies separately on the swan's- 

 down. The frame is removed, and the square of swan's- 

 down with its burden placed in one of the travelling- 

 trays. Above the eggs is next placed a square of felted 

 moss {Sphagnum). Above the moss is placed another 

 layer of swan's-down carrying a layer of eggs, and then 

 another layer of moss, and so on, till the travelling-tray 

 is filled. The bottom of the travelling-tray is made of 

 perforated zinc, and before any eggs are placed in it, the 

 bottom is covered with a thin layer of moss. The eggs 

 thus rest on swan's-down, and are covered with felted 

 moss, a layer of which also forms the lowest and upper- 

 most layer of the tray when full. For journeys to the 

 Continent or America, unbleached lino is substituted for 

 the swan's-down, because swan's-down retains so much 

 carbonic acid that advanced embryos are asphyxiated. 

 For the Antipodes, an extra precaution has to be taken : 

 a thin layer of moss is inserted between the layer of un- 

 bleached lino and the eggs, so that the latter are in con- 

 tact with the moss above and below. The travelling-tray 

 is 10 inches square and 2\ inches deep. The trays are 

 packed in an inner box only % inch larger than them- 

 selves, and this is placed in an outer box 4 inches deeper 

 and 3 inches wider than the mner. Between the two is 

 a layer of sawdust. The outer box or case measures 

 I foot 4 inches square, by I foot 10 inches deep. This is 

 the method of packing for short journeys within the 

 United Kingdom. The boxes for foreign consignments 

 are larger, and oblong in shape ; there is a sawdust 

 space as in the boxes already described, but the trays are 

 separated by means of charred fillets, so that an air-space 

 surrounds each tray : above the pile of trays is a large 

 ice-tray, which occupies the whole of the top of the box. 

 Ova can be safely kept in one of these boxes during a 

 period of sixty days. 



In the chapter on " breeders " we have an account of 

 the most unique feature of the Howietoun establishment, 

 — the feature which entitles the place to be called a fish- 

 fariii, and not merely a hatchery. .Salmon and trout 

 eggs have been artificially fertilised and kept in hatch- 

 ing-houses by a great many pisciculturists, but never 

 before the institution of the Howietoun system has a 

 species of Salmo been treated after the same method 

 which is applied by agriculturists to domestic cattle. Sir 

 James Maitland may be said to have domesticated the 

 Loch Leven trout. He keeps them in a system of ponds, 

 where they are placed under more favourable conditions 

 than they meet with in the wild state, where they are 

 supplied with a constant abundance of food, and are pro- 

 tected from enemies. The Howietoun trout have been 

 rescued from the battle of life and subjected to the in- 

 fiuences of cultivation and artificial selection. A flow of 

 5,000,000 gallons of water per diem is made to support 

 a stock which produces 20,000,000 ova annually. The 

 original stock of breeding-fish was raised from eggs taken 

 at Loch Leven in 1874. As the fish grew older the size 

 of their eggs increased, the fry from these ova were 

 bigger and stronger each season, and it became evident 

 that the ova of old trout were much the most valuable. 



