of the Fishery Board for Scotland. 



119 



warded by rail to Aberdeen. On arrival the barrel was, by inadvertence, 

 sent to the cold store, the temperature of which was 20° F. ( — 6*6° C). 

 Twenty hours later it was recovered from the cold store. By this time a 

 layer of ice 2| inches thick had formed on the top of the sea-water. The ice 

 was removed, and the barrel was then conveyed to the Laboratory. After 

 an interval of one to two hours the spawn was, at 3 p.m. on September 13, 

 distributed in several hatching-boxes supplied with running sand-filtered 

 water of a temperature of about 12° C. 



The first portion of the spawn had been in the barrel for five days, and a 

 large quantity of it was alive. The embryo was at the stage shown in 

 fig. 10 ; the tip of the tail almost reached the head. Some of the eggs of 

 the later portion of spawn were alive and in the disc stage. 



On September 19 a quantity of herring fry was noticed. Some may 

 have appeared before that date. There was a strong current of water 

 flowing through the boxes. The temperature of the water in the pond at 

 the Laboratory had been in the interval — September 12 to 19 — at 11 *6° 

 to 13° C. That range may be taken for the water flowing in the hatchery. 

 The fry were swimming actively right at the surface, so close to it that they 

 continually broke the surface, causing a rather characteristic shimmer. 



Some embryos showing pigmented eyes but not yet ready to hatch 

 probably belonged to the second batch of eggs. Many of the eggs were dead ; 

 one mass consisted of dead eggs except at the edge, where one egg contained 

 a live embryo ready to hatch. This fact would probably indicate that the 

 mass belonged to the first portion of spawn. Many of the eggs had died 

 before the closure of the blastopore. Some, however, had died after the 

 embryos had developed. 



There were large quantities of fry for a week after September 19. The 

 majority of the eggs were, however, dead. 



Meyer's Experiments. 



Meyer* made some important experiments on the influence of cold on the 

 incubation-period of the ova of the spring-herring of the Baltic (Kiver 

 Schlei). 



" The eggs, fertilized in porcelain dishes on April 26, were kept at various 

 temperatures ; the water was changed once a day. The ova kept at 10° to 

 12° C. hatched in 10 to 11 days. Those that were put on arrival at Kiel 

 into water at from 1° to 2° C, and which were kept at that temperature, 

 hatched out in 28 to 33 days. Some were still later in escaping. Some 

 eggs of the summer-herring had, however, been retarded to a similar extent 

 by a temperature of 3*5° 0." 



" In the case of eggs kept at 0° C-, the first fry appeared on the 47th day. 

 The fry did not seem to be quite healthy, although many of them swam 

 actively about all day long. Some of them had curved backs. Meyer, 

 however, was of the opinion that healthy fry might be hatched at a tem- 

 perature of 0° C. The limit to which cooling of the ova may be carried, 

 without causing death, is given by Meyer, for the Baltic water, at between 1 ° 

 and -0-8° C. ; in either case near 0° C. In water of -0*8° C. the yolk 

 becomes opaque and the egg-shell swells up and bursts. He found that the 

 fry of the spring-herring, which measured on hatching 4*7 to 7*2 mm., were 

 rather smaller than those of the summer-herring, which varied from 5*4 to 

 8*8 mm. In each case the eggs which had the longer incubation-period gave 

 rise to the larger lava. The water of the Schlei when fertilization was made 

 on April 26 had a salinity of 1 per cent. The water in Kiel harbour had 

 about that time a salinity of 1*4 per cent." 



* Meyer — " Biologische Beobachtungen bei Kiinstlicher Aufzucht des Herings der 

 westlichen Ostsee." Mittheil. aus der Komm. zur wissenschaftl. Untersuchung der 

 deutschen Meere. I. Berlin, 1878. 



