The Retardation of the Development of the Ova of the Herrimj. 9 



The Cvrrent of Water. 



I think that the current of water should be strong. It is not 

 necessary that it be continuous : it may be intermittent. A large 

 quantity sent through the apparatus at intervals would probably be 

 more effective than a small continuous current. 



The Filter-Barrel. 



During the experiment, the filter-barrel, in which was filtered the 

 water that was cooled, was allowed to work for 40 days. This was 

 probably an error. Whether it affected the success of the experiment 

 is doubtful. It would be better to have the filters frequently cleaned. 



Experiments with Spawn from Live and Dead Herrings. 



On Qalvamized Wire Gavze and Glass Plates. 



A number of ripe herrings were put into a herring barrel and sent 

 to Aberdeen. On arrival all but two were dead. The survivors were 

 a male and a female. The herrings had been probably not more than 

 12 hours in the barrel. Four experiments were carried out on March 

 24th 1911. 



(A) Some spawn was obtained from the two live fishes and it was 

 put on a piece of galvanized wire gauze. The gauze was new, but it 

 had been for a daj^ or two in running .sea-water. The eggs appeared 

 to do well for a few days. Thej^ showed lots of crystals. The eggs 

 gradually died off, and on the 25th day after fertilization all but three 

 were dead. The embrj^o at that time showed black pigment in the 

 eyes. 



(B) Spawn and milt obtained from dead herrings were put on 

 narrow-meshed galvanized wire gauze in hatchery water. The eggs 

 developed for a time, but by the 20th day all but one or two were dead. 



(C) Spawn was obtained from a dead fish and put on a glass plate. 

 This spawn was put into the water in which the herring travelled to 

 Aberdeen. No fresh milt was supplied to the water. I examined a 

 drop of the water : tailed sperms were visible, but thej- showed little 

 motion. Fertilization ensued, however. Although most of the eggs 

 died off, two which had embryos ready to hatch were found alive on 

 the 31st day. A good number of the eggs had died after pigment 

 had began to show in the eyes of the embryo. 



(D) Some spawn and milt were taken from dead herrings and put 

 on a glass plate in new (hatchery) water. Fertilization took place in 

 this case also. Many of the eggs had well developed embrj'-os, but 

 most died before hatching. 



The four lots of spawn stood, after being prepared, for some hours 

 in still water. The}' were then all put in a revolving tin box set in a 

 galvanized iron tank. The water supplied to them was cooled. The 

 temperature is given in the column marked "Tin " (p. 5) from the date 

 March 26th onwards. One egg which had been in still water all night 

 showed a large normally segmented disc and a huge quantity of 

 crystals. Some fry were got from the spawn on the 26th to 31 days 

 after fertilization. 



