432 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [6] 



It seemed very surprising that no floating cod eggs bad been found, 

 although at that period some of these fish had not finished spawning. 

 When I took some cod-eggs and impregnated them, it api)eared that they 

 did not float either, but sank to the bottom like the eggs of the plaice. 



This discovery made new investigations necessary, but these could not 

 be made till the spring of 1882. I impregnated the eggs of cod, plaice, 

 and flounder ; and bj^ keeping, by means of ice, the temperature of the 

 water at 4° — 8° Celsius, and by keeping the water in motion through a 

 glass funnel drawn up and down, I succeeded in hatching a number of 

 young fish. At some future time I intend to give a full report of their 

 development ; and so I will only state here that plaice and cod were 

 hatched in about fourteen days and flounders in eight days. IMy diag- 

 nosis of the previous year was, therefore, entirely confirmed. It ap- 

 peared, however, that the capacity of the eggs of these three kinds of 

 fish for floating in the water is limited and varies very much. Inconsid- 

 erable fluctuations in the saltness of the water are suflicient to cause the 

 fresh-laid eggs either to rise or sink. Moreover, when the saltness of the 

 water is not verj^ great, many impregnated and developed eggs sink to 

 the bottom after a short time; whilst all eggs which have either not be- 

 come impregnated, or which have ultimately died, always sink to the 

 bottom. 



The "way the eggs would act could not be stated beforehand with such 

 certainty as peoi)le will be inclined to suppose. There was no fact 

 to indicate that the capacity for floating of the eggs, which frequently 

 contained a great deal of oil, was very small, and adapted itself so little 

 to external conditions. As matters stood, a more thorough examination 

 of this subject appeared to be of practical and scientific interest. I 

 therefore deem it proper to give exhaustive statements relative to the 

 weight and number of the eggs — statements which for the present may 

 appear, perhaps, too detailed. 



B. E. Earll* has given us an excellent treatise containing full data 

 relative to the cod, the plaice, and the Oadus poUachiiis. From his ex- 

 periments in impregnating fish-eggs it appears that invariably only a 

 certain quota of the total number of eggs contained in a fish could 

 be successfully preserved. Thus, for instance, of a fish containing 

 2,700,000 eggs, only 400,000 eggs, or one-seventh of the entire quantitj^, 

 could be preserved ; the remainder matured later and were discharged 

 in the hollow of the ovarium. Earll comes to the conclusion that, in 

 such a fish, about 337,500 eggs matured per week, and that its spawn- 

 ing period lasts two months. Ho also shows that all fish ultimately 

 discharge all their eggs. The mature eggs of a cod weighing 75 

 pounds would Aveigh about 45 pounds ; and it is impossible that any fish 

 could at one and the same time contain this quantity. 



I have no objection to these important observations, as all my ob- 



* Uuited States Commission, Fish and Fisheries. Report of the Commissioner, 1878. 

 Part VI, p. 685. 



