24 



will do the same for them, and enable them to be grown success- 

 fully without nitrogenous manures ? 



A brief discussion followed, in which Dr. FitzGerald, Mr. Walton, 

 and others took part, and a cordial vote of thanks to the President 

 for his excellent paper was passed. The next meeting will take 

 place on the first Tuesday in November, when Mr. Henry Ullyett 

 will read a paper on the " Evolution of the Horse." 



A short discussion ensued and a hearty vote of thanks proposed 

 by Dr. Fitz-Gerald was carried. About sixty members were present. 



NOVEMBEB 13th, 1891. 

 Fifty members and friends were present. The following paper 

 on the Life History of the Fresh Water Hydra, written by Miss 

 Knight was read by Mr. Knight. It was well illustrated by 

 diagrams and was followed by a discussion. 



THE FRESH-WATER RYDUA— Hydra viridis. 



There is an old story of the Greeks, in which we were 

 interested in our school days, which tells us that there was a 

 celebrated monster to which the name of Hydra was given which 

 infested the neighbourhood of Lake Lerna. It had a hundred 

 heads according to Diodorus, and as soon as one was cut off two 

 immediately grew up unless the wound was cauterized. It was 

 one of the labours of hi ercules to destroy this monster, which he 

 .accomplished. 



The modern hydra probably obtained its name from this fable, 

 hut it was quite a different sort of animal, although at one time its 

 ;story created as much excitement in the scientific world, as that 

 of the monster Hydra could have done amongst the Greeks. The 

 little animal to which this name is applied can be regarded as the 

 type of the third sub-kingdom of animals, that known as 

 Ccelenterata ; which include jelly fishes and sea-anemones, animals 

 Iiaving a stomach cavity and a body cavity as an out-growfch there 

 from, and a radiate symmetr}^ ; also a mouth bordered with 

 tentacles armed with thread cells. It is very commonly found in 

 ponds and ditches, adhering to aquatic plants. If a tuft of water 

 crowfoot be placed in a vessel of water exposed to the light it is 

 most probable that in half an-hour we should see the Hydra in its 

 native element. It does sometnnes attain nearly an inch in 

 length, but is rarely more than half an inch, it possesses a 

 cylindrical body having a mouth at one end, and a disc at the 

 other for voluntary attachment. Around the mouth are 6, 7, or 

 even 10 slender contractile arms, radiating from the body like a 

 star, moving up and down in all directions, and then retracting 

 until the animal seems to be a mere mass of jelly ; then in an 

 instant all is activity again. 



