TENTH ANNUAL MEETING. IT5 
This presumption can be set aside only if male eels shall here- 
after be found among the fish which are caught in the upper 
part of rivers in the condition of young fry. 
Concerning another important fact which is connected with 
the movements of the young fry of the eel, I became acquainted 
last year (in the course of an exploration of the waters of the 
district of Konitzkunde) with the river Brahe, at Muhlhof, 
above Rittei, where a high dam was built in 1846 and 1847 for 
the purpose of watering a large system of meadows by the over- 
flowing of the stream. Below the dam is an inclined plane 
(constructed of boards), about 300 feet long, built for the pur- 
pose of preventing the water, which rushes out when the sluice- 
gate is opened, from washing away the bottom of the stream and 
its banks. This plank floor consists of two layers, the lower 
one of 2-inch, the upper one of 3-inch boards. The grade of the 
dam at Muhlhof (33 feet 3 inches) has entirely cut off the ascent 
of the fry of the eel into the upper part of the Brahe and the 
lakes tributary to it, and the number of eels caught above the 
dam—which was formerly very considerable—has become 
reduced almost to nothing. In the year 1847 the construction 
of the dam and.the inclined plane was completed; in 1852 the 
upper layer of the planks on the plane had warped and sprung 
up in many places, so that it had to be torn up for repairs. The 
cause of the warping was immediately discovered: thousands of 
eels—as thick as a man’s finger—somewhat flattened in shape, 
and, on account of the absence of light, of a pure white color, 
filled the space between the two layers of planks, and their 
united pressure from beneath had caused the upper layer to 
yield; these eels had found their way between the boards as fry, 
where they had found sufficient food and had grown to such a 
size that the pressure of their united strength had pushed up the 
roof of their prison. These facts, observed by an old millwright, 
were communicated to me by Privy Counsellor Schmid, of 
Marienwerder, who supervised the construction of the Muhlhof 
dam, and he fully confirmed them. 
Eels of 4 inches in length, which in May are plenty in fish- 
ponds, by the end of October reach a length of ro inches and 
the thickness of a man’s little finger; in the following fall they 
