12 



Appendices to Thirteenth Annual Report 



other organs of the viscera showed from this time forward no great varia- 

 tion in weight, the flesh of the fish, assuming they do not feed in fresh 

 water, must subsequently be the source from which the material is 

 taken for the construction of the ovary. In order to ascertain whether 

 this was the case, he conducted a series of most careful investigations. 

 He states that the results of these investigations show that for every 

 lb. that the ovaries increase in weight, between the beginning of August 

 and the 12th October, more than a lb. of flesh disappears; and that the 

 loss of albumen from the lateral muscles, during this period, is sufficient 

 to supply the last four-fifths of the growing ovary. 

 Pood of During the four years in which Professor Meischer Ruesch was 



Salmon. conducting his investigations he looked almost in vain for signs of any 



food in the stomachs of salmon. Only in the case of one small spent 

 male did he find the remains of two partly digested fish, probably roach. 

 Dr Hoek's experience seems to have been somewhat similar. Out 

 of 2000 specimens examined he found the remains of food in only seven. 

 These seven fish were taken in March and April, and had their genital 

 organs very slightly developed. Both observers found that the stomach 

 walls of the salmon taken in the river were contracted and wrinkled, and 

 presented a strong contrast to the wide distended stomach of the North 

 Sea or Baltic salmon. They both, therefore, formed the opinion that 

 salmon ceased to feed after they entered freshwater. • Professor Meischer 

 Ruesch was further of opinion that his chemical investigations of the con- 

 dition of the stomach fully established this theory, although he admits that 

 ' necessity, which can break iron, may teach an occasional male salmon to 

 £ feed, while the female, whose return journey has commenced (December 

 ' to the beginning of February), finds a kind of nourishment in the absorp- 

 ' tion of numerous (sometimes several hundred) not yet ejected eggs.' 

 With regard to the nourishment of salmon when in fresh water, some 

 very interesting investigations were made. If it is the case that salmon 

 remain in fresh water, without taking food, from the time they enter the 

 river until the following autumn or winter, as Professor Meischer Ruesch 

 considers his investigations prove, those entering in winter, when their 

 ovaries are only one-sixtieth of their ripe weight, must have in themselves 

 a greater reserve of food to sustain life during their long sojourn in 

 the river than those entering in the summer or autumn ; that is to say, 

 fish of the same length would weigh more or less according to whether 

 they were taken entering the river early or late in the season. To 

 ascertain whether this was the case, Dr Hoek weighed and measured a 

 number of female salmon taken in Holland about the 8th January, and 

 divided them into groups according to their length — the difference in 

 length of the fish in each group not exceeding one centimetre. The aver- 

 age weight of each group was then calculated. He repeated the same 

 observations with salmon of precisely the same length taken about the 

 8th June. A comparison of these observations show that salmon taken 

 in June were, on an average, 7 per cent, lighter than those of the same 

 length taken in January. Professor Meischer Ruesch' s investigations in 

 this direction show that the salmon taken near Basle about the middle of 

 October were, on an average, about 6 per cent, lighter than those of the same 

 length taken in the beginning of August. 

 Sex of salmon Professor Meischer Ruesch noted the sex of the salmon he examined 



entmonths fter ' durin g Jnl J aild the four following months in 1878 and 1879. He 

 refers to the fact that, among clean salmon taken in the early part of the 

 year, males can hardly be distinguished from females, as males at that 

 time have bright shining scales, roundness of body, and short snouts 

 without a trace of hook-like form. He considers that it is not until April 



