160 
PACIFIC SCIENCE, VoL VII, April, 1953 
late autumn. In both cases Asplanchna priodon- 
ta and Keratella cochlearis were found abun- 
dantly. The length of the posterior process of 
the latter species varies greatly, showing stages 
almost continuous from to typica- 
type (Fig. 2). Polyarthra trigla shows a very 
wide distribution (Fig. 3). In the specimens 
from Seiko, two varieties were included (var. 
major and var. remata). 
Of 17 species reported by Hada (1936) 
from this lake, 7 were also obtained in the 
present survey. They belong chiefly to the pe- 
lagic species, while the remainder are those 
of the creeping type. The occurrence of such 
bottom-inhabiting forms may be attributed 
to vertical hauls. The total number of species 
recorded from this lake is 28. This is the 
greatest number of species found in any single 
locality in Korea. 
Seventeen species were found in two collec- 
tions from Kanggyong. One collection from 
a small pond (8^) contained 13 species. Of 
these, Brachionus calyciflorus shows great vari- 
ability, many types such as typica, amphiceros, 
amiraeiformis, dorcas, and spinosus being iden- 
tified. Another collection from a pond (8i^) 
contained 10 species, of which 7 are also 
found in pond 8^?. No remarkable morpholog- 
ical characteristics can be found. 
In the eastern region, the greatest number 
of species was found from Kangdong-po 
(9^, b, c). The total here is 23, if Sato’s (1941) 
record is added. The present collections were 
made from a small boat at three stations on 
the lake. Notholca occur in all three stations, 
Notholca acuminata in the first and third sta- 
tions, and Notholca lahis in the second. These 
species have been known as brackish-water 
forms and were also found in Lake Kam-ho 
( 12 ). 
Of eight species found in Kam-ho, six are 
also found in Kangdong-po. 
The remaining two localities are located in 
the far southern region of eastern Korea, near 
the coast of the Japan Sea. An unnamed pond 
is situated to the west of the Bukkokuji rail- 
way station (14). Its area is considerable and 
it receives several brooks from the rice fields 
around it. Eight species were found both in 
the collections from the surface and in those 
from the bottom, the total being 14. There 
are two common species in these two places, 
one pelagic and the other a creeping species 
— Keratella cochlearis and Diurella tigris. 
Throughout all the regions surveyed, the 
species belonging to the genus Keratella occur 
most frequently. The features of its distribu- 
tion seem to be characteristic. Keratella coch- 
learis in both forma typica and var. tecta is 
distributed in the northern, middle, and east- 
ern regions, whereas the remaining forms 
seem to be limited to a single region. K, 
quadrata, K. serrulata, and K. cochlearis var. 
macracantha are distributed chiefly in the 
northern region, K. cochlearis f. micracantha, 
K. valga f. asymmetrica, and f. monstrosa in the 
middle, and K. cruciformis var. eichwaldi and 
K. valga f. tropica in the eastern region. K. 
quadrata was, however, found also in the 
western region, and its forma asymmetrica has 
been recorded by Sato (1941) as a summer 
plankton animal of Kangdong-po. 
It is remarkable that the distribution of spe- 
cies of southern origin, such as K. valga f. 
tropica, have shown a late autumn occurrence 
in the district of the Japan Sea coast. This 
suggests that the influence of the northward- 
flowing warm current along the coast of 
North Korea upon the climate of this district 
may be one of the factors acting in the distri- 
bution of this species. It is also interesting 
that, in spite of the collections having been 
made in the northern region in summer and 
in the southern region in late autumn, K. 
quadrata appears to be distributed strictly in 
the northern part and K. valga only from the 
southern region (Fig. 2). 
Species belonging to the genus Brachionus 
occurred in comparatively few places. Two of 
theso localities were the stations in and about 
the city of Seoul where the collections were 
made by Sato. In the present survey, Brachi- 
onus species were found in only three locali- 
ties, i.e., Kanggyong, the Kangdong-po, and 
