L78 



Part III. — Seventeenth Annual Report 



Bosmina longispina. — The Bosmina from Loch Ness exhibited some* 

 variation in size and in the length of the antennules and posterior spines, 

 but appeared to belong to the same species. They also appeared to show 

 a certain amount of seasonal variation, for it will be observed that while 

 they were 44 common " or "abundant" in gatherings collected in August 

 1897 and 1898, they were decidedly scarcer in those collected during the 

 la;e autumn and winter months. 



Alonopsis occurred on two of the dates mentioned, and on both occasions 

 in gatherings collected with a fine silk tow-net off Castle Urquhart, 

 and both were surface gatherings. Only one specimen of Alonopsis 

 was observed in each of the gatherings. 



Polyphemus pedieidus.—\t would seem, from an examination of the 

 Table, that seasonal changes affect to some extent the distribution of this 

 Cladoeeran; it was not observed in the gatherings collected in December 

 and January, nor in those collected in October 1897 ; it was rare in 

 those collected in October 1898, while in those collected in August 1897 

 and 1898 it was more or less frequent. It occurred in gatherings 

 collected at 60 fathoms, and from that depth to the surface, but was 

 more frequent in those from the lesser depths. 



Bythot replies longimanus. — This had a distribution somewhat similar 

 to Polyphemus. 



Leptodora hyalina.—T\iQ distribution of Leptodora, like that of some 

 of the others, appeared to be affected to some extent by the changes of 

 the seasons; it occurred all over the loch, and in almost all of the 

 gatherings, but it was most common in those collected in August 1898. 



(2) Loch Oich. 



Loch Oich is situated along the watershed of the Great Glen, and is 

 the highest of the three lochs under discussion. It is much shallower 

 than Loch Ness or Loch Lochy, and its bottom is very irregular; its 

 surface is also broken up by several islands. Its present level is about 

 100 feet above the sea at ordinary high water. Being smaller and more 

 sheltered than either of the other two lochs, its range of temperature is 

 greater, the water in summer being warmer and in winter colder, and 

 probably this may have a tendency to react on the more susceptible of 

 the invertebrate inhabitants of the loch. The examination of the tow-net 

 gatherings has not, however, brought out any very marked differences ; but 

 further reference will be made to this point under " Notes on the Species" 

 at p. 186. A series of temperature records will be found in the 

 following Table. 



Table showing Records of Temperature Observations taken at 



Loch Oich. 



Date. 



Hour. 



Temperature. 



Wind. 



Surface Movement 

 of Water. 



Air. 



Surf. 



Water. 

 5Fms. 



ISFms 



Direction. 



Weather. 



Force. 







Degs. 



Deg*. 



Begs. 



Degs. 









1897. 

















Aug. 6 



Noon. 



64-0 



65 -0 



62-0 



4!>-0 



S. W. 



M drate. Hazy ; rain. 



Moderateiy rough. 













10 fms 





Dec. 7 



2.15p.m. 



48-2 



43T 



429 



42-9 





Squally.; Heavy rain. 



Rough. 



1898. 













Aug. 4 



9.30a.m. 





59-5 



59-0 



59-0 



W. S. W; 



M'drate.j Cloudy; show- 



Slight ripple. 

















ery. 





Oct. 6 



3.7 p.m. 



GO -2 



55-5 



52-3 



52*3 



E. 



,, j Fair ; clear. 



Strong ripple. 



