[37] BIOLOGY OF THE RHINE SALMON. 463 
October on in larger numbers, and are nearly every year caughtin small 
numbers near Basel in November; they are fat fish, with red flesh, and 
fetch 24 to 3 times as high a price as the spawning salmon. These fish, 
with their diminutive testicles and ovaria, have by many people been 
considered as a sort of barren variety of the salmon. But I have said 
before, that already during the first spring months, March and April 
(when the salmon increase in number), the ovaria increase arithmetically 
slow, but in a very considerable geometrical progression, until the large 
schools of summer salmon, which appear from May till July, show them- 
selves as the undoubted candidates of the next spawning season. Soon, 
however, no former winter salmon can be distinguished from the sum- 
mer Salmon, at least not by any less development of the sexual organs. 
If we observe these winter salmon closer—from November to March— 
we are first of all struck with the fact that, with few exceptions, they 
are very large fish, belonging as to length to the fish of maximum length, 
and to the second half of the third curve (length exceeding 860 milli- 
meters). Also the Dutch fish—January and beginning of March—of 
which I have measurements, were, with few exceptions, within the same 
limits of size (861 to 970).* Among 99 Rhine salmon, the sex of most 
of which had not been determined (there being no decided difference of 
nose between males and females), from the months of January to March, 
1878 to 1880, only five measured between 835 and 860 millimeters, whilst 
all the others measured more (as much as 975, and one even $90 milli- 
meters); whilst during May and June, 1878 (just as in 1879), the salmon 
of the second curve came in large numbers, the St. Jacob’/s salmon mak- 
ing their appearance from July on. 
By comparing nine winter salmon, which (by opening them) have 
been found to be females, and which are all of one and the same size, 
with the highest average weight (of a group) of the next division or 
group, comprising salmon of the same size, I found (although there are 
of course slight differences of shape) an excess of average weight over 
the summer salmon (June, July, and August) amounting to 990 grains, 
or 10 to 11 per cent. 
That this cannot merely be ascribed to differences of ‘‘shape,” but to 
an accumulation of reserve matter will be seen by a determination of 
the muscles of the pectoral fin of a Basel female salmon, made on the 
5th April, which show these muscles to weigh 3.06 per cent. of the weight 
of the entire body (these same muscles in a Dutch salmon of March 15, 
weighing very nearly the same, viz, 3.03 per cent.), whilst otherwise 
the weight of these same muscles in eight Basel salmon (excepting, how- 
ever, the strange fish caught August 1, 1879) varied between 5.54 and 
* As higher prices are paid in the Dutch markets for large salmon than for small 
salmon, while in the Basel market there is no such difference, no mercantile interests 
can here come into play. 
tCould this fish (length 940 millimeters, entire weight 11,130, and weight of ovarium 
808 grams) be an individual which was intended for a winter salmon, but which im- 
migrated too late? ’ 
