A LECTURE 



DELIVERED BY 



J. JENNER "WEIR, Esa., F.L.S., 



President of the West Kent Natural History, 3Iicroscopieal, and Photographic 

 Society, 



At the Ckystal Palace Soiree, November 6th, 1872, 



ON 



"THE AQUARIUM AND ITS INHABITANTS." 



The aquarium in this building has now been open to the public 

 since 22nd August, 1S71. The perfection of the an-angements 

 for insuring the health of the marine animals, which will survive 

 in confinement, has now been put to the test of experience ; and I 

 therefore have had the greatest pleasure in responding to the 

 wish of the Directors that I should on this evening give a lecture 

 on the subject. 



But before proceeding further, I wish to define what an 

 aquarium really is. 



All breathing animals breathe air, but in two different ways. 

 Those that breathe by lungs oxygenate their blood by the oxygen 

 contained in the atmospheric air drawn into the lungs ; those 

 that breathe by gills oxygenate their blood by the oxygen con- 

 tained in the air always existing in water in its ordinary state ; 

 and some of the lower forms of life appear to be able to oxygenate 

 their circulating fluids by simple, exposure of the surfaces of their 

 bodies to the water, but have no organs differentiated for the 

 purpose. 



An aquarium, therefore, is intended only for those animals 

 which, in ordinary language, breathe or sustain life by absorbing 

 the oxygen contained in the air always found in the water ; and 

 although a tank may be used for an anilnal that breathes the 

 atmosphere, a tank made for such a purpose is no more an aqua- 

 rium than is the tank in which the Hippopotamus bathes at the 

 Zoological Gardens. In such tanks the water can never be kept 

 in a pellucid state, and in most cases the body of the animal 

 immersed is invisible, owing to the turbid state of the water. 



You will thus- at once understand why an elaborate and ex- 



