20 oe Fresh Water Oligocheta. [ZOE 
66. GLYCERIA FLUITANS R, Br. Denver. 
67. GLYCERIA PALLIDA Trin. Denver. 
68. GLYCERIA GRANDIS Watson. Denver. 
69. AGROPYRUM GLAUCUM R. & S. var. OCCIDENTALE 
V. &S. The Common Blue-Stem. Denver. 
70. AGROPYRUM TENERUM Vasey. Denver. 
71. Elymus Virginicus 1. var. submuticus Hook. Denver. 
RESTRICTED DISTRIBUTION OF FRESH WATER 
OLIGOCHATA. 
BY GUSTAV EISEN. 
The geographical distribution of fresh water oligocheta, as 
compared to fresh water algze, is most interesting and unexpected. 
It is well known that a majority of species of fresh water 
algze are cosmopolitan, and even locally widely distributed, 
being rarely confined to special localities, such as a single pond, 
spring, or lake. An alga which is found in one spring or creek 
is almost certain to be found in some other spring or creek in the 
vicinity. Many species have a world-wide distribution, while 
others of rare occurrence have been found in distant localities. 
With the fresh water oligochzeta this manner of occurrence is 
exactly opposite. Few species are found in countries far apart. 
Not one species is found distributed all over the world, while by 
far the greatest number of species are endemic in certain districts, 
or even confined to certain ponds, lakes, rivers, creeks, or springs. 
outside of which they do not appear to thrive. With the genera 
this, of course, does not hold good. ‘True, Lumbrici are found the 
world over, but it is more than probable that whenever the same 
species is found in very distant countries, it has been artificially 
introduced there with economic or garden plants brought along 
by nursery men or horticulturists. The distribution of fresh 
water oligochzta is as yet only imperfectly known, and it is 
too early to compile their geographical distribution, but enough 
is known to warrant us to believe that there are some powerful 
influences in nature which operate on and curtail their 
