Introduction. 3 
breadth of 12 miles. The total area is 269 square miles. The southern region of the 
lake is shallow and weedy, but the greater part of the northern region is over 200 
feet deep and towards the north end there is a pocket of considerable size in which 
the depth slightly exceeds 300 feet. The water is remarkably clear and free from 
sediment and its temperature, considering the latitude, is high. No part of the lake 
ever freezes. The bottom is sandy in some places and at others muddy. There are 
a few small rocky islands, but the greater part of the shore is low. The river known 
at its exit as Seta-gawa, and at its mouth (at Osaka) as Yodo-gawa, connects Lake 
Biwa with the Inland Sea of Japan, but there is no definite evidence that the lake ever 
opened directly into the sea, from which it is about 40 miles distant. 
The fauna of the deeper parts of the lake, as was proved by my dredgings and 
will be shown in papers included in this volume, differs considerably from that of 
shallow water. There is also a distinct fauna associated with stony and rocky 
ground at the margin and round the islands. 
The Tai-Hu. (Fig. 2, p. 4). 
The Tai-Hu or Great Lake lies in the alluvium of the delta of the Yang-tse 
Kiang about 40 miles inland from the sea in a direct line. It is connected by numer- 
ous creeks and canals with the vast water-system that has been linked together for 
the last seven centuries by the Grand Canal of China. The lake is very shallow, 
the depth, so far as is known, nowhere exceeding 12 feet. The bottom is com- 
posed at most places of soft mud and the water is full of suspended silt. The length 
of the lake is about 60 miles and the breadth about the same. No details are known 
of the temperature of the water, but it is decidedly lower than that of Lake Biwa. 
I was able to investigate only a small part of the Tai-Hu, but obtained indica- 
tions that the fauna was remarkably uaiform; the course of my short trip is indicated 
on the map (fig. 2) by a dotted line. The most interesting feature in the fauna, so 
far as can be seen at present, is the existence of a distinct marine or estuarine 
element, though the water is of course quite fresh. 
The Tale Sap. (Fig. 3, p. 6). 
The Tale Sap— a name that means in Siamese " Great Lake," just as Tai-Hu 
does in Chinese— differs from both Lake Biwa and the Tai-Hu in opening directly 
into the sea. In some respects it closely resembles the Chilka Lake on the east coast 
of India, but differs in that a considerable part of its water remains fresh or practi- 
cally fresh throughout the year. It is divided into two distinct regions connected 
only by narrow channels. In the northern or inner part of the system conditions are 
almost normally lacustrine, while the outer or southern part is subject to great varia- 
tions in salinity, but probably, except in heavy floods, contains at all seasons water 
that is distinctly brackish. 
The whole lake-system is about 50 miles long. The water is shallow, the depth 
probably not exceeding 16 feet at any point in the inner lake. In the channel north 
