

The Journal 



OF THE 



Postal Microscopical Society. 



DECEMBER, 1882. 



®n tbe Structure anb leconomi? of 

 tbe 2)apbnla* 



THE PEESIDENTIAL ADDRESS. 



By Arthur Hammond, Esq., F.L.S. 



'*2lfe^ 



Plates 18 and 19. 



PURPOSE to utilize the few moments which 

 custom places at my disposal for the Presidential 

 Address, by endeavouring to impart such informa- 

 tion as lies in my power, on what may indeed be 

 described as one of the commonest of common 

 objects of the microscope. 



The genus Daphnia, pre-eminently among the 

 microscopic Entomostraca, is a favourite with every 

 tyro in microscopical science. This arises, firstly, 

 from its abundant distribution, seven species being found in our 

 own country, some of them swarming in every piece of water 

 whither microscopists are wont to resort ; secondly, from its 

 singular form ; and thirdly, from the facility with which every 

 portion of its organization can be made out, through the 

 transparent cuticle in which it is enclosed. I trust, therefore, that 

 the observations I shall make to-night may prove of general interest. 

 The articulate plan of structure common to all arthropods is 



N 



