of the Fishery Board for Scotland. 



151 



species of Moll us ca, i.e., Pisidium and Limnwa, but they were very 

 scarce. The Crustacea were also individually scarce, though a considerable 

 variety of them were obtained. The total number of the species of 

 Eutomostraca observed in each gathering, and also the number belonging 

 to each of the three groups represented, are shown in the annexed 

 formula: — Co., Copepoda; Os., Ostracoda; CI., Cladocera. 



Date, - 



10th Sept. 1897. 27th Nov. 1897. 



16th Mar. 1898. 



28th June 1898. 



Groups represented, 



Co. Os. CI. 



Co. Os. CI. 



Co. Os. CI. 



Co. Os. CI. 



Number of Species in 

 each group, 



9 0 11 



10 6 5 



7 5 3 



6 0 12 



Total Number in each 

 gathering, 



20 



21 



15 





The number of species of Cladocera is considerably larger in the 

 gatherings collected in September and June than in those collected during 

 the colder months ; but as regards the Copepoda the reverse of this is 

 observed, though the difference is not so great. A somewhat similar 

 difference is observed in the gatherings collected in Loch Arklet. 



(4) Loch Achray. 



The normal level of Loch Achray is stated to be two hundred and 

 seventy-six feet above the sea, or eighty-eight feet lower than the level of 

 Loch Katrine.* It appears to be nearly of the same size as Loch Arklet, 

 but it differs considerably not only in its elevation, but also in its sur- 

 roundings. It has been remarked that Loch Achray appears to be merely 

 an expansion of the River Teith ; and it is also probable that, at a com- 

 paratively recent period, it was smaller in size and stood at a lower level 

 than at present. If any good map of the district be examined, it will be 

 observed that at a short distance from the east end of the loch the River 

 Teith is joined by the Finglass — a stream which takes its rise ten or twelve 

 miles to the northward, and which, flowing down Glen Finglass, drains a 

 considerable portion of the neighbouring uplands. This stream debouches 

 from Glen Finglass almost at right angles to the bed of the Teith, and 

 where it enters that river it makes a slight bend to the west. Between 

 this point and the east end of Loch Achray the Teith has very little of a fall; 

 and thus it happens that when the Finglass, swollen by heavy mountain 

 rains, comes down in flood, the current of the Teith is sometimes overpowered 

 and the water is forced back into Loch Achray, which, in consequence, 

 rises at such times more or less above its normal level. Moreover, the 

 Finglass will also, when in flood, carry down from the hills considerable 

 quantities of debris — such as sand and gravel, branches, and roots of 

 trees — which will no doubt have, within certain limits, tended to obstruct 

 the bed of the River Teith, and thus gradually, and more or less perma- 

 nently, to raise the level of the loch beyond. 



* It may also be stated that, according to the reduced Ordnance Survey m p, 

 present level of Loch Vennachar is only six feet below that of Loch Achrav. 



