14 



HYDEA 



It is uncertain, however, how far these species are really 

 ■distinct from one another, and the following description will 

 apply to any of them. 



Fig. 11. — Hydra. A diagrammatic longitudinal section of a specimen 

 with ripe reproductive organs, and with a fully-formed bud ; x 12. 

 (a. m. m.) 



A, mouth. B, hypostome. O, enteron, or digestive cavity. D, ectoderm. 

 E, supporting lamella. "P, endoderm. ■ (j, cavity of one of the tentacles. 

 H, testis. I, ripe ovum in the ovary. K, fully-formed bud, with mouth and 

 tentacles. L, foot by which the Hydra is attached to a piece of weed. 



I. EXAMINATION OF A LIVING SPECIMEN. 



Gut off .a small piece of weed with a Hydra attached to 

 it ; place it on a slide in a drop of water, and put on a cover- 



