of the Fish<T// Board for Scotland. 



165 



The number of species belonging to each of the three group- of 

 Entomostraca represented in the Table will be more clearly understood 

 when arranged as in the annexed formula, where Co., = Copepoda, 

 Os., = Ostracoda, and CI., = Cladocera. 



Dates. 



June, 

 1890. 



Sept. 3, 

 1897. 



Dec. 16, 

 1897. 



March 3, 

 1898. 



June 13, 

 1898. 



Names of the Groups, 



Co. Os. CI. 



Co. Os. CI. 



Co. Os. CI. 



Co. Os. CI. 



Co. Os. CI. 



Number of Species in each 

 Group, 



9 17 16 



10 7 14 



11 9 8 



7 10 1 



14 10 14 



Total Number in each 

 gathering, 



42 



31 



28 



18 



38 



The Cladocera, as a whole, were scarcer in those gatherings collected in 

 the colder months than in the others. It may also be stated that in 

 March the level of the water was much higher than during any of the 

 other visits, and this no doubt accounted, partly at least, for the great 

 scarcity of Cladocera in the gathering collected at that time ; the reduced 

 temperature incidental to the season may also have had some influence in 

 bringing about this result. 



(7) Duddingston Loch. 



Duddingston Loch, situated on the south side of Arthur's Seat and 

 immediately south-w 7 est of the village of Duddingston, is of small dimen- 

 sions, being a little over five hundred and fifty yards in length by about 

 tw r o hundred and forty yards in breadth at the widest part. Its elevation 

 above the sea is about one hundred and fifty feet. The loch is shallow, 

 and therefore its temperature is more readily influenced by the changes 

 incidental to the different seasons ; it is quite a common experience 

 to find that in winter its surface has been transformed into a thick sheet 

 of ice, while in summer the water may be so warm as to be almost tepid. 

 Such extreme variations in the temperature of the water are here of yearly 

 occurrence, and appear to be the rule rather than the exception, and it 

 was thought that it would be of interest to ascertain what was the 

 effect of such extreme variations of temperature on the invertebrate fauna 

 of the lochj as well as upon the micro-algae. 



The loch was examined by tow-net on four different occasions — viz., 

 on 15th December 1897, and on 2nd March, 15th June, and 16th 

 September 1898. Two other attempts were made to tow-net the loch, 

 but these failed. One of the failures was due to the surface of the water 

 having become frozen over during the previous night ; on the second 

 occasion the observations could not be made owing to stormy weather. 



In addition to the four visits which I have referred to, a portion of the 

 shore of the loch was also examined on the 1st of September 1897, the 

 results of which are incorporated with those obtained in connection with 

 the other visits, so far as they relate to the shore fauna. 



