434 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [8] 
Basel spawning salmon* have again reached the sea about the middle 
of January, and if we, moreover, take into consideration the period of 
migration from Holland up the river, I feel justified in maintaining that 
the large majority of our Basel salmon stay in the Rhine between 6 
and 94 months, a small number staying 94 to 12 months, and a few even 
15 months, their sexual organs developing all this time, whilst they 
abstain from all food. I cannot, of course, positively deny that, in 
exceptional cases, a few individuals return to the sea in an immature 
condition; but nothing which has come under my observation points in 
that direction. ; 
I shall also, for the present at least, be careful not to apply my data 
to the Lower Rhine. As I have not been able to observe the Dutch and 
North Sea salmon during this season of the year, I cannot decide 
whether, as Barfurth says, numerous large salmon in an almost mature 
condition immigrate from the sea late in summer and during autumn. 
All I maintain is this, that such belated immigrants, with the exception, 
perhaps, of a few male fish, do not come up as far as Basel. 
The great differences in the degree of development of the sexual 
organs I interpret as indications of the dates of immigration. The 
later immigrants very possibly have entered upon the first stage of their 
ovarian development whilst still in the sea,t but still they seem to lag 
behind the earlier immigrants, and only catch up with them very grad- 
ually, but under all circumstances by the time the spawning season 
commences. ‘Thus, two Dutch salmon had, on the 31st May, 1879, 
ovaria weighing 0.61 per cent. of the entire weight of the body, there- 
fore less than half the weight of the ovaria of Basel salmon of the same 
period. The smallest fish furnished particularly numerous instances of 
this catching up of the young with the older immigrants. On the 19th 
of August, 1879, I found in three small salmon from Wesel ovaria weigh- 
ing 0.56 and 0.80 per cent. of the entire weight of the body (therefore 
corresponding to the Basel March and April salmon) and testicles 
weighing 0.91 per cent. of the weight of the body, therefore correspond- 
ing to the Basel June testicles. The hook-formation (according to 20 
measurements of the length of the nose) had been decidedly retarded. 
Five weeks later another batch of fish of the same size from Wesel 
*Mr. Glaser supposes that the time occupied by the salmon in returning is very 
short, because, owing to the impetus which they receive, many of them land on sand 
banks and in shallow places, and thus fall into the hands of man. 
+tHow far this development has advanced can only be decided by data from the 
Lower Rhine. How many per cent. of the total weight of the body are occupied by 
the ovaria of salmon caught near the mouth of the Rhine from the beginning of May 
tillthe middle of June? How many per cent. of the male organs from May till the 
middle and end of July? So far, only one individual (caught August 1, 1879) has 
give rise to the suspicion that it had finished a considerable period of its ovarian 
development while in the sea. This fish (differing in this entirely from other fish 
caught at the same time) had an ovarium weighing 7.2 per cent. of the total weight 
of the body, and muscle-flesh containing much (18.7 per cent.) albumen and fat. 
