of the Fishery Board for Scotland. 



137 



surface water, has so far only been able to a small extent to affect the 

 under-surface water, but though, as the heat continues, it may not greatly 

 increase the surface temperature, its influence extending downwards 

 gradually raises for a considerable distance that of the under-surface water. 

 The difference between the temperature at the surface and at ten fathoms 

 on 29th June 1898 was 10*8 degrees; but on the 20th August 1897 the 

 difference was only 5*1 degrees. By the time November is reached the 

 summer heat has given place to colder weather, and one of the results of 

 this is that the surface temperature of the water is lowered and becomes 

 more and more uniform with that of the water beneath the surface. As 

 the winter advances it tends to reduce the temperature of the water still 

 further ; but though the lowest readings of the present series of observa- 

 tions are those taken in March, it is probable that the average lowest 

 readings may occur earlier in the year. Definite information on such 

 points would, however, require a special and lengthened series of 

 observations. 



At the lower end of the loch the water, being comparatively shallow, 

 did not show the same amount of variation between the surface and under- 

 surface temperatures in August and June. The surface temperature was 

 rather lower in March, but slightly higher for the other months. 



v 



Pelagic Entomostraca Captured by the Toiv-Nets. 



Free-swimming entomostraca did not appear to be very plentiful in 

 Loch Lomond, and they were less frequent in November and March than 

 in August and June. Fourteen species were obtained in the tow-net 

 gatherings collected during the four visits to the loch, but only a few of 

 the species occurred in all the gatherings. The two tow-nets already 

 described were used, and gatherings were collected to the north of Balloch 

 Pier, off Balmaha, and off Inversnaid. The following Table contains the 

 names of all the species captured by the tow-nets, and the localities and 

 dates where they were obtained. 



[Table. 



