The morphological development, growth and change in distribution pattern of the Ayu-fish in Lake Biwa were studied. In the earlier phases when the body form variation is not so clear, the distribution of the larvae is passively determined by water current. The differentiation in the body form starts with the further developed larvae and they aggregate around the subaqueous terrace. As the differentiation becomes clearer, the fish can be clbssified into two groups by their body form, i.e., the running water type and the standing water type. The former migrates toward the littoral area while the latter remains in the deeper part. The relation between morphological development and growth reverses itself at about this phase ; the fish of the running water type which have been "more developed but less grown" in the preceding phases become "less developed but more grown" in the subsequent phases, and vice versa with the fish of the standing water type.
There are many physical factors in ecology influencing the desert lizards, but the role of temperature is of great importance because the environmental temperature controls the degree of their activities to a large extent and imposes limitations on their movements and distribution. Ophiomorus streeti is a desert dweller fossorial by habit, but, like other terrestrial lizards, it does not hibernate but remains buried in the loose sand in a state of torpor during winter and emerges occasionally to search for food, restricting thereby its activity within a tolerable temperature range. Though much work has been done in regard to temperature responses in reptiles-COWELS (1940 & 1941), COWELS & BOGERT (1944), BOWERS & SMITH (1947), NEIL (1948), BOGERT (1949) & FITCH (1954,1955,1956) etc., thermoregulation in burrowing forms, like Ophiomorus, is still to be studied. Therefore, this paper contributes to our knowledge on the temperature responses in this lizard. The experiments were conducted in 1968 at Jodhpur in Western Rajasthan (India), an are a in the southern part of this province insufficiently watered and unproductive but abounding in sand dunes was chosen for study. Experiments were conducted both, in nature and in captivity. The mean maximum temperature in Jodhpur is 25.9℃. and the mean minimum temperature is 10.4℃. during winter and 37.9℃. and 15.8℃. during post monsoon. The average rainfall is 366mm. Experimentally, the optimum temperature for the lizard was 29.0℃±1.5℃ and the lethal 44.0〜47.8℃.
Analyses was made of the variation of the individual growth and growth compensation observed in the "hasu" in Lake Biwa, on the materials principally collected from the spawners during the six years from 1963 to 1968. The age and body length at each age were estimated by the annual rings on the scale. The variation in individual growth of the first year of life was relatively small. The differences of hatching period, increase of variation of body length immediately after hatching, the variation with beginning of feeding, and the differences in feeding condition, were considered as the factors of this variation. The variances of body length at 1+ tended to decrease in the warm season and to increase in the cold season. This increased value was much the same as the variance at age II. The growth compensation was observed in the growth of the third year of life (between ages II and III). In previous studies made by many workers, this phenomenon was considered to be produced either by 1) the characteristic of the growth curve itself or 2) the difference in the time when fish reach the first maturity which depresses the growth. These two mechanisms are discussed in relation to the growth compensation observed in the "hasu."