102 Fart III. — Twenty-seventh Annual Beport 



spawned for three-and-a-half hours. Some plates were filled with ova, and 

 fertilization was attempted with maisie herrings of both sexes that had been 

 dead for six hours. The later history of this lot is not known, as they 

 became mixed with the preceding plates of Lot II. 



The barrel containing the cases was headed up at 6 p.m., and it was 

 unpacked in the Laboratory 19 hours later. The water had been unchanged 

 during that period. 



III. The third lot of eggs was got at mid-day on February 19 from two 

 live herrings, a female 25 cm. long and a male 28*8 cm. in length. The 

 milt was squeezed out in a coherent ribbon. Three plates were filled. The 

 plates were allowed to remain for one hour before they were packed in the 

 barrel. Some of the milty water was put into the barrel. The barrel was 

 unpacked 7| hours later. 



IV. Spawn was obtained at St. Monance at 1.30 a.m. on February 28 

 from live and dead females. The milt was obtained from live herrings. 

 Both the milt and the eggs ran more freely than during the operations a 

 week previously. The barrel was packed at l.'dO a.m., and unpacked at 

 Aberdeen seven hours later, or 13 hours after fertilization. The water had 

 only been changed once, that was when the barrel was packed. 



V. The fifth lot of spawn was among gravel. A thick layer of gravel was 

 put into a barrel, which was taken to sea in a fishing boat. The spawning 

 was carried out by one of the crew. The milt was pressed out of a living 

 male herring into a bucket of water. The living females were pressed in the 

 barrel of water. Some milt was added from the bucket with each female 

 spawned. An attempt was made to distribute the spawn over the gravel. 

 The eggs falling to the bottom became attached to the gravel and formed big 

 masses of eggs stuck together, or remained unattached single eggs. The 

 eggs were spawned between 4 a.m. and 5 a.m. on March 5th, and the con- 

 signment arrived at the Laboratory about 9 p.m. on that day. 



As the weather was cold at this time, no arrangements were necessary in 

 the case of any of the consignments to guard against any possible rise in 

 temperature during the journey. 



It is important at all stages to have good clean water for the eggs. Mud 

 sticks closely. It may sometimes be removed partially by means of a brush 

 or a little jet of water. 



In transferring the plates of eggs from one receptacle to another, and also, 

 later, when examining the eggs, it was necessary to expose them temporarily 

 to the air. This is probably a disadvantage, although no harm was clearly 

 traced directly to this cause. Every plate has been in this way exposed to 

 the air. In future arrangements this should be avoided. 



The sixth lot of spawn was obtained in September. It was, like the last, 

 mixed with gravel. The barrel was forwarded without any cooling arrange- 

 ments. It arrived on September 12th. On that date the temperature of the 

 air was at one time 15 "2° C. 



On arrival at the Laboratory the eggs were not, as a rule, transferred 

 directly to the cooled water. They were usually left a night in the wooden 

 cases in running water. Then they were distributed in the cooled boxes, or 

 in water of the ordinary temperature. The water supplied to the hatchery at 

 this time of the year was cold, sometimes being below 4° C. On February 

 28, 29, and March 1, the temperature of the water on each date fell to 

 between 2° and 3° C. 



The spawn on the glass plates was at first put into the egg-boxes (E, in the 

 accompanying wood-cut). The glass plates are there shown inclined in 

 position, with the eggs on the under side. 



The water supplied to the eggs, uncooled and cooled, was filtered through 

 sand. Several filters were made of herring barrels, as shown in the sketch. 

 On the bottom was set a layer of large stones, covered by a layer of pebbles. 



