100 On tin' Tratujunt of Hirrliuj Spaictt 



deficient aeration, but I have also thought that they were in sonic way 

 due to the galvanized metal. They did not however appear in all the 

 eggs of a plate: they occurred in both living and dead eggs. They were 

 observed in certain of the eggs of a plate which was rotated. In one 

 instance the crystals appeared in the egg within ?}i\ hours after fertiliza- 

 tion. 



The layer of eggs was, towards the end of the period of incubation, 

 often attacked by a fungus. The mould grew in water of 37^ to 43" F. 

 Whether it was the cause of the death of the eggs, or whether it grew 

 there in consequence of the death of the ova I was unable to decide. 

 It probably was instrumental in killing some of the eggs. Diatoms have 

 also grown on ova exposed to strong light ; it is better therefore that the 

 eggs be screened. 



Mr Anderton used tanks of wood, coated with asphaltum. 1 now 

 think that earthenware vessels would be preferable for the spawn. 



How far sterilized water would be an advantage is uncertain. Stone^ 

 preferred for his successful transport of fishes and lobsters across the 

 American continent, sea- water which had stood for two or three weeks 

 covered and perfectly still, to sea- water that had been boiled. "At the 

 end of the three weeks the miscroscopic creatures will be found at the 

 bottom of the tanks, in the form of a deposit of slime. The water above 

 will be perfectly sweet and clear, and it will remain so indefinitely." 



I think however that there is reason to doubt that the environment 

 is the sole cause of the death of the ova. It seems to me that the eggs 

 differ in vitality. It is noticeable that about 48 hours after spawning, 

 the eggs on the plates very often look well: with very few exceptions 

 they are fertilized. One might infer then that all that was necessary, 

 was to provide a suitable environment, in order that all may eventually 

 hatch. The eggs however gradually die of?: a certain proportion survives 

 and hatches. Any difference of environment of the ovum due to its 

 particular position on the plate, or the fact that two or three other eggs 

 crowd it closely, cannot surely, except in a few cases, account for its 

 death. The eggs of fishes are known to exhibit very great vitality. Roth 

 pelagic and domeisal eggs arc recorded as having been frozen and still 

 they hatched out, after thawing. 



In the case of artificially spawned eggs one may argue that the ova, 

 on being pressed out of the fish, may receive slight mechanical injury, 

 which does not inhibit fertilization, but only permits development up 

 1() a (•('itiiin point. 



» Stone. Tifporl U.S. Fish Commission, 187!) (1SS2). 



