of the Fishery Board for Scotland. 105 



Lot I., the embryos were further advanced, because it was in the cooled water 

 for a shorter time (see Table, p. 106). 



March 11. — In Lot I. the little fish was well formed: the eyes were 

 pigmented black. The tip of the tail came round to near its origin from the 

 yolk sac (tig. 11). One embryo examined was in a less advanced condition ; 

 the eyes were not pigmented. The only pigment visible in the embryo at 

 this date was in the eyes. There were little colourless patches all over the 

 head. The heart was beating slowly. 



March 16. — The stage arrived at by Lot I. is shown in Fig. 12. The 

 embryo, which was now nearly ready to hatch, was lively. It twisted itself 

 about like an eel inside the zona. The heart was beating, and the long 

 points from which the yolk is absorbed were visible on the anterior end of 

 the yolk mass. There was a green iridescence in the dark eyes. 



March 19. — The first fry (fig. 55), only a few in number, were obtained 

 on this date from Lots L, II., and III. Hatching had taken place from each 

 plate, after a period of incubation of 29 days in the case of the first two and 

 of 28 days in the case of Lot III. In estimating the time of incubation, a 

 new larva found on any date will be regarded as having been hatched on the 

 previous day. The plates were examined. Lot I. contained the largest 

 quantity of dead eggs ; Lots II. and III. were in better condition. Several 

 fry hatched out while the plates were being examined — most from Lot III. 

 Although the eggs of Lot III. were the dirtiest, that plate contained the 

 smallest number of dead eggs. Up till this date a strong current of water 

 was flowing through the box. The egg when ready to hatch is translucent 

 and colourless except for the two opaque silvery eyes, which show as dark 

 points. 



March 20. — A large number of fry was obtained. 



March 22. — A few more fry appeared on this date. 



March 23. — About 40 larvae had hatched out since the previous day. A 

 good deal of fungus had appeared on the plate of Lot III. 



March 24. — Some fry had appeared since the day before. The plates of 

 these lots had patches of fungus on them, and most of the eggs were dead, 

 apparently just lately. Some of the eggs were still alive. 



March 25. — Two larvae were got on this date. 



March 27. — The plates of eggs were taken out and examined to-day. 

 The plate of Lot I. was well covered with a thin scum of mould. The 

 fungus could be lifted off in a matted sheet. There was a large proportion 

 of the total quantity of eggs on the plate still adhering dead. A good pro- 

 portion of these contained well-developed embryos, the tail being fairly long. 

 Some had died when ready to hatch. The fungus is a mass of delicate 

 hyphse (figs. 13 and 14). There are also present on the shells of the dead 

 eggs the round white granular masses found on the eggs in the cooled 

 water (PI. I., fig. 57). In h and c (fig. 13) are given enlarged drawings of the 

 hypha in which granules were arranged in little box-like collections. A 

 spindle-shaped body shown in a (fig. 13) was observed floating about ; it 

 was a little broader than one of the hyphse. Lots II. and III. were 

 similarly attacked. Lot II. had very few eggs, but they were covered by 

 the matted fungus. The extensive destruction of the eggs and the appear- 

 ance of the fungus had occurred since the previous examination of the 

 plates on March 19. Did the fungus cause the death of the eggs or did it 

 develop after they had been otherwise killed ? The current of water flowing 

 through the ova had been decreased, and this may have acted injuriously 

 on the eggs. Although it is possible that when the fungus had obtained a 

 good footing, it might of itself prove the destruction of the eggs still alive. 



The empty egg-capsule, from which the larva has issued, has sometimes 

 merely an irregular tear across it ; at other times a piece has been taken out 

 completely (fig. 17). 



