170 



Part III — Seventeenth Annual Report 



normal level that parts of the road that exter.ds along its west side were 

 submerged and rendered impassable for foot traffic. In July, on the other 

 hand, the loch was so low that numbers of " islands," which in 

 ordinary circumstances are under water, as well as a considerable part of 

 the shore, were exposed ; and these extreme conditions in the physical 

 aspects of the loch would no doubt affect in a greater or less degree the 

 distribution of the invertebrate fauna. 



The following Table shows the temperature readings obtained on each 

 of the four occasions when the loch was examined : — 



Date. 



Hour. 



Temperature. 



Wind. 



Weather. 



Surface Movement 

 of Water. 



Air. 



Surf. 



Water. 

 30 Ft. 





Direction. 



Force. 







Degs. 



Degs. 



Degs. 













1897. 





















Sept. 16 



11.30 a.m. 





53-4 



53-2 





Westerly. 



M'd'rate 



Cloudy; showery. 



Slight ripple under 





















shelter of land. 



Dec. 10 



11.30 a.m. 



38-8 



39-0 



39-0 





S. E. 



Squally. 



Showers of sleet. 



Rough. 



1898. 









41ft. 









Mar. 31 



11.30 a.m. 



51-0 



39-0 



39-3 





Westerly. 



Light. 



Cloudy, hut fine. 



Slight ripple. 











25 ft. 











July 6 



1 p.m. 



65-0 



58-1 



58-0 





W. by W. 



Squally. 



Dull ; inclining 



Moderate. 













to rain. 





In this loch the water at surface and bottom was of a nearly uniform 

 temperature on each of the four occasions when I examined the loch, and 

 the water was neither so cold in winter nor so warm in summer as that 

 of Duddingston or Forfar Lochs. The difference between the surface 

 reading on 31st March and 6th July is 19*1 degrees, while the difference 

 between the bottom readings for the same periods is 18 7 ; the tempera- 

 tures for December and March are practically the same ; while the 

 readings for September are fully degrees below those for July. 



The Pelagic Fauna taken in the Tow-Nets. 



The true pelagic Entomostraca of Loch Doon, as in the other lochs 

 examined, comprised comparatively few species. The seasonal distribution 

 of one or two of them exhibited more or less marked variation, while 

 others appeared to be less subject to seasonal influences. Two of the 

 Entomostraca obtained in the tow-net gatherings collected here — viz., 

 Diaptomus laciniatus and Daphnia nasuta — have not been found in any 

 of the other lochs; further reference is made to these under "Notes on 

 the Species." The following is a full list of the Entomostraca captured in 

 the tow-nets : — 



[Table. 



