JACOBY'S JOUENEY TO COMACCHIO. 653 



Konitzkunde) with the river Brahe, at Muhlhof, above Rittel, where a high dam was built in 1846 

 and 1847 for the purpose of watering a large system of meadows by the overflowing of the stream. 

 Below the dam is an inclined plane (constructed of boards), about three hundred feet long, built 

 for the purpose 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 two-inch, the upper one of three-inch boards. The grade of the dam at Muhlhof 

 (thirty three feet three 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 mill- 

 wright, were communicated to me by Privy Councillor Schmid, of Marienwerder, who supervised 

 the construction of the Miihlhof dam, and he fully confirmed them. 



Eels of four inches in length, which in May are plenty in fish ponds, by the end of October 

 reach a length of ten inches and the thickness of a man's little finger; in the following fall they 

 measure from twenty to twenty-four inches, and in the third year are ready to be eaten. On 

 account of their rapid growth and hardy nature, in consequence of which latter they live in mud- 

 holes and unprofitable waters of all kinds, the breeding of Eels is a very remunerative business. 

 The young fish (of which, at the time of their first appearance at the mouths of rivers, it takes 

 1,500 to 1,700 to make a pound, while, when taken later and a little farther from the sea, it takes 

 only 350 to 400 for the same weight) may be obtained at low prices from France through Hiiuingen, 

 or in Germany from Randesberg, and, through the Berlin Aquarium, from Wittenberge, and, when 

 the temperature of the air is not too high, may be carried in soft moss throughout all Germany. 



According to the statement of the well-known Paris fish-merchant, Millet, two pounds of 

 Eels, planted in a muddy pond in 1840, in five years yielded 5,000 pounds of fine Eels. 



JACOBY'S TOUR TO COMACCHIO IN 1877, AND HIS CONCLUSIONS. " In the fall of 1877," writes 

 Jacoby, "I undertook a journey from Trieste, by way of Ravenna, to Comacchio. Convinced of 

 the difficulty of the questions to be solved by my own previous labors, I had not great hopes of 

 finding sexually mature Eels, either gravid females or mature males. My highest aim was at 

 the beginning to determine the following points: (1) "Whether evidences of preparation for breed- 

 ing might not be found in the Eels which were wandering in the fall toward the sea; (2) to what 

 extent Eels with the organ of Syrski could be found participating in this migration; (3) as far as 

 possible to obtain Eels from the sea at a distance from the coast in order to compare their organs 

 of reproduction with those of the Eels in the lagoons. 



"In determining the answers to the first two questions I was able to make some new and inter- 

 esting discoveries, but with regard to the latter, my most diligent efforts were absolutely fruitless. 



"I found that the Eels when migrating to the sea in the fall took no food. In many hundreds 

 examined by me, caught during their movement, I found stomach and intestines entirely empty; 

 that the Eels during their migrations eat nothing is also known to all fishermen and watermen of 

 Comacchio. At the same time, the Eels which remained in the lagoons were more or less filled 



