[7] BIOLOGY OF THE RHINE SALMON. 433 
somewhat earlier. Beginning on the 20th of October, some seed may 
be squeezed out of a few, and from the Ist of November out of nearly 
all normally-developed males, which, however, cannot be considered ag 
a sign of absolute maturity in the whole organ. All the data relative 
to the spawning season of both sexes have been fully corroborated by 
Mr. Glaser. 
To return to the development of sexual maturity, it is very instructive 
to compare the respective tables with the following table, showing the 
monthly results of the fisheries in the Rhine between Basel and Lau- 
fenburg: 
TABLE III. 
nent aaace | | Average of all 
the year, there | 1872. | 1873. | 1874. | 1875. | 1876. | 1877. | 1878 | 1879, | the monthly 
were caught in oer cr aie 
the month of— | Woe Se 
alle i 7 | al ee an 
Jannary-ae2cccssedlecsctcce | 0.58 | sees 0.14] 0.08| 0.61) 016] 0.49 | 0. 28 
February ..----.--- esti PnONOBsIC aS -k, rw pen 1.35| 0.32| 0.49 0.29 
March ......-.....- 1.60| 273| 0.36| 0.19! 0.55) 371| 1.69] 1.26 1.45 
Agia tes ke 1.52/ 219] 5.41| 0.371 234] 303| 3.98] 1.36 2. 52 
iyeeiiast secs: 4.57| 7.77| 5.78] 2.12| 4.72| 5.86] 804| 2.04 5.11 
iti ea 11.36| 18.77| 27.36] 13.40| 5.89| 15.99| 14.96°| 7.57| 14.24 
ices ew 91.32 | 17.97| 1834] 10.05| 19.57| 29.38| 19.32| 11.36 18. 41 
August d..2-.-4-.+ 10.78 | 7.18| 14.24] 12.01] 8.62] 10.18| 10.59| 24.08) 12.21 
September ......-.- 13.70 | 16.08] 19.64| 814] 29.94] 17.18] 1609| 21.46| 17.69 
October .....-..... 15.70 | 14.62/ 1.88| 24.80| 19.18] 3.17| 17.24| 19.42 14. 50 
November .-..-.... 15.06 | 9.69) 3.10| 20.89] 7.25] 4.45| 5.81| 9.03 | 9. 41 
December ......... 4.98 | 2.37 | 3 s3| 665| 2.57| 5.79| 2.59| 1.46] 3.7 
If, really, as Barfurth supposes, the spawning salmon ascend the river 
from the sea only a short time before the spanwing season, ‘‘ with eggs the 
size of peas,” why does the large increase in the number of salmon caught, 
amounting to six times that of April, appear in June and July, at a time 
when the ovaria have reached 1.3 to 5.3 per cent. of the total weight of the 
body—therefore only about 5 to.22 per cent. of their weight when fully 
matured—and not in September and October? Do these July salmon 
make way again for other salmon? If, furthermore, in August and Sep- 
tember, there is in the Rhine a mingling of returning salmon and new 
immigrants, why did the‘individual differences in the weight of the 
ovaria decrease instead of increase? 
I am therefore of opinion, and shall adduce further proof of my asser- 
tion, that our winter salmon, which arrive in the neighborhood of Lasel 
Jrom November to March, remain in this neighborhood all during summer 
and autumn, and that they reach their sexual maturity gradually, in com- 
mon with the large schools of later immigrants, which begin to ascend the 
river from May on, so as to spawn at the same time, from the middle of 
November till the middle of December. My. His, in his varied observa- 
tions, has reached the same opinion.* 
If we suppose, by way of approximation, that the majority of the 
*T, § 25. 
S. Mis. 29 28 
