22 



Part III. — Twenty-eighth Annual Report 



Uneooled Spawn. 



Two days after fertilization those of the plates which were examined 

 looked well. The eggs were in disc stage. Where they were thickly 

 arranged the eggs were polygonal-shaped through mutual pressure. One of 

 the plates showed white powdery patches of excess milt, which could be 

 brushed off. One or two dead eggs were visible. Many herring scales were 

 attached to the eggs of one of the plates. 



Plates 18 and 20 were fixed on two of the external surfaces of a cubical 

 wooden frame, which floated freely in the tank. Plates 12 and 16 were put 

 inside an open frame, which was anchored immediately under the inflowing 

 current. Plate 13 was transferred to a metal box supplied with running 

 unfiltered water. This plate at the expiry of a further 22 days was covered 

 with a thick layer of mud. Most of the eggs had died at the stage of the 

 closure of the blastopore. The live eggs which contained embryos ready to 

 hatch were located at the margin of the plate, or scattered here and there on 

 the outside of the thick layers of eggs. 



10 days. — Plates 18 and 20 showed a good number of dead eggs. Live 

 eggs were in the stages where (a) the tail first projects as a little process, and 

 (b) where the end of the tail nearly reaches the head. No crystals were 

 observed in the eggs. Plates 12 and 16 had a large number of dead eggs. 



20 days. — On plate 20 the majority of the eggs were dead. I was able 

 to detect only a few live eggs ; they were near the margin of the plate. 

 Many of the eggs had apparently died early. 



25 days. — Plate 20 had a few eggs alive ; they seemed ready to hatch. 

 Almost all the eggs were dead. 



26 days. — All the eggs of plates 12 and 16 were dead except a few round 

 the margin. Some of the eggs had hatched. 



27 days. — Plate 18 had some eggs alive ; some had hatched. 



34- days. — Some living unhatched eggs were found on plates 16, 18, 

 and 20. 



Plates 14., 15, 17, 19— Cooled Eggs. 



Two days after fertilization certain of the plates were examined ; the stage 

 of development was that of the solid disc. The eggs all looked well On 

 plate 19 there were some patches of milt among the eggs. They were partly 

 brushed off. 



Plates 14, 15, and 17 were put into the frame B, which was rocked till 

 the tenth day. Thereafter it revolved. 



10 days. — Plates 14, 15, and 17 showed a lot of dead eggs. The eggs 

 stuck directly to the glass were not so bad. The live eggs, which are at the 

 stage where the blastopore is closing or is just closed, look well. There were 

 lots of crystals inside the eggs. Plate 15 did not show so many dead eggs. 

 Most of the eggs were alive. Dead eggs were scattered here and there, mixed 

 with live, among the eggs which were isolated, or in a continuous single- 

 layered stratum, as well as where the ova were more than one layer thick. 

 The general distribution of the dead eggs throughout the plate would suggest 

 that they had been unfertilized, or had suffered some injury during the 

 spawning operation. This criticism may be applied to all the lots of eggs. 

 Numbers of minute active infusors were running about over the eggs of plates 

 14, 15, and 17. 



The embryo has sufficient room inside the egg to float about. When the 

 egg is rotated the embryo, under the influence of gravity, alters its position 

 and comes to rest again. 



20 days. — Live eggs were visible all over plate 14. One showed the tail 

 as a little process. Crystals were seen in both live and dead eggs, but not 

 in all the eggs examined. 



