146 



Part III. — Seventeenth Annual Report 



found in each of the four gatherings. The following abbreviations are 

 used in this formula: — Co., Copepoda; Os., Ostracoda; and CI., Cladocera. 



1 Date, .... 



9th Sept. 1897. 



26th Nov. 1S97. 



15th Mar. 1898. 



27th June 1898. 



; The groups represented, 



Oo. Os. CI. 



Co. Os. 01. 



Co. Os. CI. 



Co. Os. CI. 



No. of Species belonging 

 to each group, - 



7 4 20 



S 6 11 



7 5 5 



3 3 11 



Total No. of Species in 

 each gathering, 



31 



25 



17 



17 



The differences in the numbers of the species belonging to each of the 

 groups, as brought out in the formula, may partly be accounted for by 

 the difference in the time of the year when the gatherings were collected. 

 Some of the species are probably more local than others in their distribu- 

 tion, even in the same loch ; and as exactly the same parts of the shore may 

 not have been examined on each of the four visits, this also may to some 

 extent account for the differences referred to. It may also be stated that 

 very feAv molluscs were observed in auy of the gatherings collected here. 



(3) Loch Katrine. 



According to the reduced Ordnance Survey map, Loch Katrine is 

 about eight miles in length, and has an average width of about three- 

 quarters of a mile ; and if a line be drawn from Trossachs pier at the 

 lower end to the upper end where the stream that flows down Glen Gyle 

 enters the loch, it will be found to stretch in a direction nearly W.N.AV. 

 ^ W. The loch has a somewhat serpentine form, so that, while the upper 

 half curves slightly to the south of the line I have indicated, the lower 

 half bends nearly as much to the north. Moreover, if a line such as that 

 suggested be drawn between the two ends of the loch, it will be found 

 that the point where it touches the north shore is almost midway 

 between the upper and lower ends. The normal level of Loch Katrine, 

 as stated on the map, is three hundred and sixty-four feet above the sea, 

 or about one hundred feet below the level of Loch Arklet ; even the 

 bottom of Loch Arklet at the deepest part is nearly forty feet 

 above the surface of Loch Katrine. Loch Katrine is very deep in 

 some parts • it would appear from the latest soundings that in Scotland 

 the only lochs that exceed it in depth are Loch Morar, Loch Ness, and 

 Loch Lomond. 



Loch Katrine was tow-netted at both the upper and lower ends during 

 September and November 1897, and March and June 1898. The 

 steamer that plys on Loch Katrine in connection with the summer traffic 

 is aid up during the winter and early spring months, and thus it is not 

 so convenient in the winter season to get to or from the upper end. But 

 on the two occasions when I visited the loch in November and March, 

 Mr. Dunsmure whose kindness I have already alluded to, sent his yacht 

 to Stronachlacher and conveyed me thence down the loch to the 

 Trossachs pier. 



