20 



Part lit. — Twenty-eighth Annual Report 



Three lots of spawn were secured. The eggs were attached to glass plates. 



The first lot, consisting of Plates 1-4, was obtained at Anstruther on 

 February 24th, 1910. The herrings had been captured in anchored nets 

 shot close to the harbour. The milt was coherent, and it was taken from 

 both live and dead males. Plates 1, 2, and 4 were filled with eggs from a 

 live female. Plate 3 received the eggs that were pressed out of a dead 

 female. The plates were kept till next day in a herring-barrel filled with 

 water. The water of the harbour was very dirty, and in consequence the 

 eggs received a coating of fine sand. The spawn arrived at Aberdeen on 

 the evening of the 25th. It was transferred to a tank (No. 2) supplied with 

 running filtered water. Two days later the plates were put into the frame A 

 in the cooled water. At this time the eggs looked alright, but a few were 

 dead. Eleven days after fertilization the eggs were in the stage of the 

 closure of the blastopore, I found no crystals in the eggs. Three days 

 later, however, some crystals were observed. At 32 days the egg examined 

 showed an embryo, the tail of which almost reached the head. No crystals 

 were made out. Two days later the plates were not looking well, and on 

 the 37th day the dead eggs were very noticeable. At 46 days some live eggs 

 were almost ready to hatch, and they showed no crystals inside the zona 

 On the following day a sample which was examined consisted almost 

 entirely of dead eggs ; some had died quite recently : they were still 

 translucent. 



On the 50th day the plates were removed to uncooled water. Only one 

 live egg was found. Some of the eggs had advanced embryos. Some of the 

 more recently dead eggs were next the glass and protected by an outer layer 

 of eggs. The live egg, which was about ready to hatch, lived till the 58th 

 day, but it was found dead unhatched on the 61st day. The eggs had died 

 off steadily during the period of incubation. 



Second Lot of Spawn. 



The second lot of spawn was procured on 25th February from herrings 

 which had been brought ashore in a barrel, and also from some herrings 

 which were taken from the hold of a fishing-boat. The females were all 

 dead ; one male was alive. 



Plates 6, 7, 8 were filled with spawn from the herrings of the shot. 

 Plates 10 and 11 received the ova from the herrings brought in the barrel. 

 They arrived at Aberdeen on the evening of the 25th and were put into tank 

 No. 2. 



Two days later Plates 6 and 10 were transferred to frame B in cooled water. 

 The eggs looked well ; a good deal of sand was present about the eggs. They 

 showed a large blastodisc. Some of the eggs had not expanded to form a 

 peri-vitelline space. 



The next day Plate 11 was put in the cooled water. It was placed on 

 edge in the bottom of the tank of cooled water, e.g., C and D in sketch. 

 There were some unfertilized eggs on this plate. They were small, slightly 

 opaquish, and showed no peri-vitelline space. An irregular disorganised 

 blastodisc was present in some cases. The fertilized eggs looked very well ; 

 they were very clean. 



At 9 and 10 days after fertilization Plates 6, 10, and 11 showed a fair 

 sprinkling of dead eggs. The live eggs were at the stage of the closure of 

 the blastopore. There were crystals on the inside of the zona of both live 

 and dead eggs. 



On the 21st day a good proportion of the eggs was dead. Two live eggs 

 on Plate 11 were in stages where (a) the blastopore was closed, or (b) the 

 tail of the embryo nearly reached the head. Eggs of a similar stage of 

 development had been found 12 days previously. During that period, viz., 

 from March 6th to 18th, the temperature of the water was very low, often 



