74 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



to plants, but are distinctly higher than the Protozoa and 

 the Sponges. A piece of one of the' " Sea-firs," or Sertu- 

 larian Zoophytes, is shown, natural size, at 3 (Sertularia 

 abietina), where each of the little angular enlargements or 

 projections on the stem and branches is a horny cup con- 

 taining one of . the members of the colony. Another 

 Sertularian Zoophyte (Sertularella polyzonias) is seen en- 

 larged in the living condition, under the microscope, at 1. 

 The little members of the colony (the Zooids) are seen 

 protruded from their delicate horny cases. Each has an 

 open mouth surrounded by about 20 delicate filaments, 

 the tentacles, by means of which the Zooid catches food 

 from the surrounding water. Each such Zooid is very 

 similar in structure and appearance to the little fresh- 

 water Hydra, and consequently these colonies are fre- 

 quently called " Hydroid Zoophytes." 



Another common and closely related kind of Hydroid 

 Zoophyte (Obelia geniculata) is seen at 2. This is called a 

 " Campanularian " Zoophyte because each cup containing 

 a Zooid is bell-shaped and placed at the end of a ringed 

 twig or handle. This figure also shows certain larger 

 cases, in which are formed special buds that become 

 detached as little glassy bells or jelly-fishes for the purpose 

 of producing and scattering the eggs that will eventually 

 give rise to new colonies. The fixed Hydroid Zoophyte 

 thus gives rise by budding to free-swimming Medusae 

 (like that shown at 10, fig. XII.) ; and the Medusa pro- 

 duces eggs which give rise to fixed Zoophytes. Such a 

 life-history is an example of ' k alternation of generations." 



Various reports upon the Hydroid Zoophytes, by Miss 

 L. R. Thornely, will be found in our volumes. Mr. E. T. 

 Browne has contributed some papers on the Medusae from 

 work done at Port Erin. 



Many of the smaller jelly-fishes of our seas are there- 



