3^o The Upper Elf Loch, Braids. [Sess. 



young for several generations, while all the time not a single 

 male may be observed. For this reason the female Daphnia 

 has been regarded as parthenogenetic. The appearance of the 

 males is not only irregular, but is also not limited to the 

 autumn and winter months, as some have supposed. As a 

 matter of fact, we have obtained them in July as well as in 

 December, and they were even more numerous in the warm 

 than in the cold months. 



The young Entomostracan is usually very different in 

 appearance from the adult, but in some groups the difference 

 is less apparent than in others. One of the most interesting 

 groups, in this respect, is that of the Daphniadas, as some of 

 them, and Daphnia especially, are subject to so much variation 

 that there is still considerable doubt as to which are species 

 and which mere varieties. Development and environment 

 appear to have a modifying influence on the form of the 

 Daphnia?, and even in some degree on their structure also, to 

 a greater extent than on almost any of the other groups. It 

 will thus be seen that the study of the Entomostraca, like 

 so many of the other departments of nature, has its own diffi- 

 culties and interesting problems, for the elucidation of which 

 patient workers in larger numbers are needed. 



In bringing these investigations to a close, we desire to 

 emphasise the benefits to be derived from a continuous examina- 

 tion of a particular loch or pond. When such an examination 

 is carried on throughout a whole year, or longer, not only 

 seasonal variations may be noted, but the various phases in 

 the life-history of a minute plant or animal come under one's 

 observation, the cycle of growth and development is usually 

 completed, and a more or less intelligent conception is gained 

 of the various complex stages through which many, if not 

 most, of these lowly organisms pass. That there must be a 

 material gain in such a mode of procedure is evident. Patient 

 observation of the processes of nature, as these go on silently 

 around us, has its valuable uses, not to speak of its fascina- 

 tions. In such a humble task as the repeated examination of 

 even a hill-tarn, lessons can be learnt which may help to 

 unlock some secret of nature never yet yielded up. 





