114 Part III. — Twenty -seventh Annual Report 



the Laboratory on the evening of the same day. They were kept in the 

 hatchery water over night. 



March 6, — The spawn was divided, part kept in uncooled water, the 

 remainder in cooled water. An egg was examined. The disc was large and 

 segmented (c/. fig. 1). 



The Uiicoolei Spaion — V. — The uncooled spawn was put into shallow 

 enamelled trays and a circular wooden tub. The water flowed through 

 these in series. The depth of water varied from half-an-inch to two or three 

 inches ; the trays were set with a slope on the bottom. The trays and the 

 tub were turned round each day so as to alter the run of the water. This 

 was done with the view of preventing the formation of dead water. 



The large pieces of spawn were kept in a floating wicker-basket and in a 

 hatching-box (p. 102). On March 26 these eggs were nearly all dead. In 

 the interior of the mass the eggs had died in the disc stage. On some of 

 the smaller pieces the embryos had been well on before death occurred, 

 having reached the stage in which the tip of the tail touched the head. 

 On March 31 all the eggs in the big lump were dead and covered with 

 fungus. A few fry had apparently been hatched from them. 



March 11. — Some of the eggs were examined. They were at the stage 

 where the blastopore is closing [cf. figs. 5, 6, 27, 51). 



March 26. — Many of the single eggs were dead. They lay on the 

 bottom packed close with other single eggs or under the gravel, and in that 

 way did not receive efficient aeration in the trays. Where several eggs were 

 stuck together the mortality was not so marked. The single eggs had not, 

 as a rule, expanded to the same extent as the eggs that were joined 

 together. Some of the dead eggs had on the zona the round white patches 

 which were noticed above, p. 107. There were numbers of Planarians and 

 swarms of infusors among the eggs. The groups attached to the little 

 pieces of stone seemed to do well. Four larvae hatched out while the eggs 

 were being shifted about. When just released from the egg the head of 

 the larva was in some cases markedly bent downwards (fig. 56). 



March 27, 28, 29. — Fry was obtained on each date. 



April 1, 4, 5. — A large quantity of fry was got on these dates. 



On April 4 many of the pieces of spawn were dead and covered with 

 fungus. In the trays the eggs have been fully exposed to the light, and this 

 may have had a detrimental effect upon them. 



April 6, 8. — On the former date a few larvae appeared, and on the latter 

 one was got. 



April 12. — Another herring had hatched out during the night. The 

 gravel amongst which the spawn was distributed was covered with a brown 

 coat of diatoms. The great majority of the eggs were dead. Some had 

 died in the early stages. The single eggs were dead in large quantities ; 

 some were black. The pieces of spawn on the top of the gravel were 

 covered with fungus. A large proportion of the eggs had died when the 

 blastopore was closing or had closed, and some were in the stage where th 

 tail reached to the nape of the neck. Death seemed to have been gradually 

 overtaking the eggs. 



April 13. — No fry was found to-day. The eggs were cleared out. 



The period of incubation had been from 21 to 37 days. 



