162 
PACIFIC SCIENCE, Vol, VII, April, 1953 
(3 buJApestLnensls ^ (^uAdrldentatus 
cadyclfloTU-s w-TceolstTls 
Fig. 4. Occurrences of the genus Brachionus in Korea. 
the Gan-o-chi. In Gan-o-chi, two species of 
Brachionus {B. urceolaris and calyciflorus) oc- 
curred, whereas in Kangdong-po only a sin- 
gle species {B. quadridentatus var. hrevispinus) 
was found. At Kanggyong two species {B. 
angularis var. bidens and B. calyciflorus) oc- 
curred; five forms of B. calyciflorus were ob- 
served in the pond along the railroad (8^) as 
previously mentioned. 
The values of the hydrogen ion concentra- 
tion of water in these places indicate that, 
although the range tolerated by this genus 
would be rather wide, the organisms prefer 
alkaline waters. This seems also to correspond 
to conditions in Korean waters, though the 
occurrences of this genus are limited to fewer 
localities. As is mentioned above, none of 
them was found in the northern region. As 
far as our collections are concerned, one spe- 
cies was found from the middle and two from 
the eastern region, a fourth was common to 
both. Besides these, two {hudapestinensis and 
forflcula) were found in the collections made 
by Sato. They are warm-water forms. Thus, a 
total of six species of Brachionus is known 
from the middle and eastern regions (Fig. 4) . 
SUMMARY 
1. Plankton collections were made in Ko- 
rea at 16 places, which may be classified 
roughly into four regions — the northern, 
western, middle, and eastern. 
2. Fifty-eight species of Rotatoria were 
identified in these collections. In addition, 
seven species can be added from previous 
records. With the addition of eight varieties 
and seven forms, plus three undeterminable 
species, the total number becomes 83. 
3. The species of wide distribution are Ke- 
ratella cochlearis and Polyarthra trigla, both in- 
cluding several varieties or forms. 
4. Species of Brachionus were found only 
in a few stations. 
REFERENCES 
Ahlstrom, E. H. 1940. A revision of the 
rotatorian genera Brachionus and Platyias 
with descriptions of one new species and 
two new varieties. Amer. Mus. Nat. Hist., 
Bui. 77: 143-184. 
Carlin, B. 1943. Die Planktonrotatorien des 
Motalastrom. Lund Univ., Limnol. Inst., 
Meddel. 5: 1-255. 
Collin, A., H. Dieffenbach, R. Sachse, and 
M. Voigt. 1912. Rotatoria und Gastrotri- 
cha. In Brauer: Die Susswasser fauna Deutsch- , 
lands. Vol. 14. 274 pp. Gustav Eischer, Jena. 
Edmondson, W. T., and G. E. Hutchinson. 
1934. Report on Rotatoria. Yale North In- 
dia Expedition. Conn. Acad., Mem. 10: 153- 
186. 
