386 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



above will be found in the circumstance that innumerable inquiries on tJie 

 subject, which, during this spring, I had addressed to many persons in 

 Prussia, Silesia, Brandenburg, and Pomerauia, were invariably answered 

 negatively. This summer, however, I have made some interesting ob- 

 servations, showing that, also, with regard to this subject the well-known 

 words of the greatest of our German poets are eminently true: ^'All 

 theory, dear friend, is gray; but green the golden tree of life." 



In my garden, which is close to my hoiise, there is a meadow in a 

 very favorable and sheltered position, which, in accordance with my 

 I)rinciple, I had for some years used as a pond, and which was now again 

 to serve for agricultural purposes. I have to go back to the preceding 

 year. In the spring of 18S0 I sowed suitable seed on the black i)ond- 

 bottom, and as early as the middle of June, I was enabled to mow the 

 finest grass at the rate of about one wagon-load per acre. The rainy 

 season, which -set in soon after June 24, lasted, with hardly any inter- 

 ruption, for seven weeks, and on tlie 14th August ended in a terrible 

 Hood, so that the beautiful meadow (10 acres in extent), which was almost 

 ready for a second harvest of hay, was, within half an hour, flooded 5 

 feet deep, causing me again to nse it as a pond. I intended to observe 

 also, in pond-cultivation, the change of matter which, on a large scale, 

 we had often had occasion to notice in agriculture. Formerly I had 

 always used the pond as a spawning-pond for carp, but now I intended 

 to use it as a pond for raising and fattening carp. As I knew the quan- 

 tity of food contained in its waters, I tliis spring stocked the i^ond 

 with about 500 carp, weighing on an average 1 to H pounds each, 400 

 Cijprinus or/us of difierent size, and a few eels, and determined to raise 

 ducks on this i)oud in the proportion of about 1 duck to each carp. I 

 succeeded very well, 300 ducks, 100 geese, and 2 swans making this 

 pond their residence for the summer. It should also be mentioned that 

 a flock of young wild ducks, which had been caught in the neighbor- 

 hood, were also quartered in this pond. 



Although there was soine danger tlfat these aquatic birds might de- 

 prive the lish of much food, I fully expected that they, on the other 

 hand, would furnish a great deal of other food for the carp. I found 

 my expectations fully realized. 



I must here remark that while, during the first months, tlie pond was 

 swarming with immense numbers of fi'ogs, both young and old, of which 

 the older male frogs caused a good deal of trouble and dauger to the 

 old carp, these frogs were in a very short time entirely destroyed by tlie 

 ducks. The croaking of the frogs which, as soon as warm weather set in, 

 might be heard all night long, was heard no more. The more food the 

 ducks received the more food also fell to the share of the fish. 



I soon discovered that there were in the water of the pond large 

 masses of spawn, both of the carp and of the Cijprinus or/us. I had suj)- 

 ])nsed that the large number of aquatic birds (about 400), especially the 

 ducks, would entirely devour the spawn. But this did not take place, 



