1902-1903-] Distribution of the Smaller Crustacea. 25 



the first visit, I examined the pond a second time : the 

 weather in the interval had been dry and warm, so that there 

 was less water in the pond than at the first visit. Under 

 these circumstances I had expected that the entomostraca 

 would have become more crowded together, and that a larger 

 gathering would thus be obtained. The actual result, how- 

 ever, was very different. Entomostraca of any kind were 

 few, and as for Daplinia, not a single specimen was got, 

 even though the pond was carefully searched. Probably in 

 this case the warm dry weather, acting on a decreasing body 

 of water, had killed them. In this connection I would refer 

 to the joint observations of Mr Lindsay and myself at the 

 Upper Elf Loch, Braids, in the years 1896, '97, and '98, the 

 results of which were communicated to the Society in two 

 papers now embodied in the Society's ' Transactions.' In the 

 second of these papers will be found a description and tabular 

 view of the seasonal variations in the entomostraca of this 

 little sheet of water — some of these variations being rather 

 remarkable.^ 



Amongst the many species met with in the lochs of Scot- 

 land, the following may be mentioned as being more markedly 

 susceptible to ordinary seasonal influences. Holopedium gih- 

 herum was common in Loch Arklet in September and Novem- 

 ber 1897, and abundant in June 1898, but not a trace of it 

 was observed on the 15th of March of the latter year. It 

 was common in Loch Achray in September 1897 and June 

 1898, but was entirely absent on November 27 and March 

 17. It was common in Loch Doon (Ayrshire) on July 6, 

 1898, but was not observed in September, December, and 

 March preceding. The same species was taken in Loch Oich 

 in August 1897 and in August and October 1898, but was 

 absent from the gatherings collected in December and January. 

 Two other species of cladocera also exhibit a somewhat marked 

 susceptibility to seasonal changes, but the first more distinctly 

 so Ihan the other. In the lochs in which they occur they 

 are usually common in the summer months, but are scarce or 

 absent in winter. 



Amongst the pelagic copepoda which I have found in the 

 lochs of Scotland, the only species which exhibited any marked 



'■ See ' Transactions,' vol. iii. pp. 375-378. 



