A FEESH WATER AQUARIUM 17 



we will therefore do no more than suggest a few points on which 

 observation is much needed. 



(1) The attention of naturalists might be directed towards the 

 pupae of many beetles, especially that of the "whirligig" beetle 

 which, according to Professor Miall, has very rarely been seen. 

 Furthermore, the various contrivances of aquatic insects for locomo- 

 tion, egg-laying, and breathing, the defences of resting pupae, and 

 so on, are all worthy of attention. For hints as to what may be 

 done in this branch of the subject, no better work can be cited than 

 " Aquatic Insects" by Professor L. C. Miall. (Macmillan.) 



(2) The habits of many water snails form a subject about which 

 little is really known. If the student keeps several paludinae (fresh- 

 water whelks) in an aquarium, and watch them from time to time, 

 he will discover that the movements of these creatures are not hap- 

 hazard but according, apparently, to certain regular instincts. It 

 is not our purpose to do more than suggest lines of observation, but 

 we may say, from personal experience, that this particular animal will 

 certainly repay observation. 



(3) The breeding habits of leeches have been but very little 

 studied. The horse-leech and one or two other common forms occur 

 abundantly in most places. 



(4) The movements of the common pond mussel have been very 

 insufficiently observed, especially the part played by the "foot." 

 Shortly after dusk will be found to be the best time for watching 

 these molluscs. The attachment of the young to other animals is 

 particularly interesting. 



These examples have been taken at random, but the student who 

 takes up the study of any particular group of animals will soon 

 realise that there is plenty for him to find out, not to mention the 

 re-discovering of facts already known. 



II B 



