BULLETIN or THE UNITED STATES FISH COMMISSION. 447 



immediate cousequcuce of this will be tliJit those aniniiils which live ou 

 tVesli or decayed vegetable matter -will disappear. In consequence of 

 this the young fry, if any is raised, is insuliiciently fed, and compara- 

 tively few tish reach sexual maturity. In this wa^' the tish of our brooks 

 and rivers are constantly decreasing, and, as we have seen, from nat- 

 ural causes, which can be misjudged only by persons who have never 

 studied the needs of fish. 



The degree to which the abundance of fish in large water areas is 

 dependent on verj' small (partly uiicroscopical) animals, which entirely 

 escape the attention of the casual observer, may be observed in the 

 large diluvial lakes in the north of Germany. Last summer I investi- 

 gated the waters of Holstein, Mecklenburg, and Pomerania, and am 

 able to state, as the general result of my investigations, that those lakes 

 which, among the rural population, had the reputation of being par- 

 ticularly rich in fish were also particularly rich in crustaceans, worms, 

 and infusoria. With a fine gauze net one can in a few minutes catch 

 myriads of small crustaceans and rotifers, so as to cover tlie bottom of 

 the net to the depth of over an inch with a thick mass consisting en- 

 tirely of diminutive animals. A person who has not seen the great 

 mass of these little animals brought up at a single haul has no idea of 

 the enormous quantity of living beings contained in a lake with an area 

 of several square miles. An inexhaustible wealth of life moves in the 

 clear waters of such a basin ; and in exact proportion to the quantity 

 of small crustaceans and infusoria will be the product of fish. 



13^.— €A£.IFOKIVIA TKOVT FOR THJB OZAKK IflOUNTAIJV BE«IOI\. 



By MARSHALL McBONALB. 



This species {Salmo irideus), which inhabits a restricted geographical 

 range on the west coast, has been largely introduced into the streams 

 of the Eastern and Middle States through the agency of the U. S. Fish 

 Commission. In the spring of 1880, 10,000 eggs of this species were 

 allotted to the Missouri Fish Commission. These were hatched out at 

 the State hatchery and the fry planted in the headwaters of the Gas- 

 conade, Osage, and other streams of Southwest Missouri, having their 

 sources in the clear, cold, large flowing springs that abound in the Ozark 

 Hills. Three thousand were planted in the headwaters of Si)ring River, 

 a tributary of the Arkansas. 



A careful inspection of the stream, made in the summer of 1885 by 

 the commissioner of Missouri and others who were familiar with the 

 appearance of the rainbow trout, showed the presence of at least three 

 generations resulting from the original plant. The largest in size 

 weighed between 4 and 5 i)ounds ; those of the second size measured 

 from 15 to 17 inches in length; while the sources of the stream swarmed 

 with thousands of the young from 4 to 5 inches in length. 



