Observations upon the Behaviour and Structure 



of Hydra. 



By 

 Sheina Marshall, B.Sc, 



Assistant Naturalist, Scottish Marine Biological Station, MiUport. 



Introduction. 



The Hydras upon which the following observations were 

 made were obtained from various sources, chiefly through the 

 kindness of Dr. Monica Taylor, from the Convent of Notre- 

 Dame. They were kept in covered, half-pint glass tumblers, 

 in water from a large tank in which there was a fair quantity 

 of weed and a variety of animal life (Isopods, Cladocerans, 

 Planarians, &c.). This was used because the Hydra would 

 not live for more than one or two days in tap-water. The 

 water was ^changed and the tumblers cleaned when necessary. 

 This was about once a week in summer, as food-remains became 

 foul very quickly then, but less frequently in winter. The 

 water was never aerated artificially. The Hydras were fed 

 on a culture of Daphnia twice a week, and the remains and 

 excreta removed, as far as possible, the following day. Under 



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