HYDRIDJE. 



last, in some cases, became encysted ; and it is not im- 

 probable that each of these fragments would ultimately 

 give origin to a polypite. 



The affinities of the Hydridae are with the Athecata, and 

 Cams includes them in this group ; but the total absence 

 of polypary, the locomotive habit, and the character of the 

 reproductive organs seem to me to entitle them to rank 

 as a distinct suborder. 



The Hydra are all inhabitants of fresh water. We know 

 little of the geographical distribution of the genus ; but it 

 occurs in North America as well as in Europe. 



For a detailed history of the Hydra, and an account of 

 the curious experiments that have been made to test its 

 powers of reparation and endurance, reference may be 

 made to the classical 'Mernoire' of Trembley*, and to the 

 works of Baker t, KoselJ, Johnston , Albany Hancock ||, 

 Laurent If, Jager**, and Eckerft- 



1. H. VIRIDIS, Linnaeus. 



POLYPES VERD.-S Trembley, Mem. 22, pi. i. fig. 1, pi. iii. figs. 1-10. 

 HYDRA VIRIDIS, Linn. Syst. 1320 ; Johnst. B. Z. 121, woodcut, fig. 28. 

 ,, VIRIDISSIMA, Pallas, Elench. 31. 



Woodcut, fig. 40. 



POLYPITES grass-green; body becoming gradually more 



* Mernoires pour servir a 1'histoire d'un genre de Polypes d'eau douce, a 

 bras en forme de cornes. 1744. 



+ An Attempt towards a Natural History of the Polype. 1 743. 



% Insektenbelustigungen, Tlieil iii. 



History of Brit. Zooph. i. 125. 



|| " Notes on a Species of Hydra found in the Northumberland lakes,'' Ann. 

 N. H. 1850. 



^[ "Eecherches sur 1'hydre et 1'eponge d'eau douce," in Vaillant's 'Voy- 

 age de la Bonite.' 



** " Ueber das spontane Zerfallen cler Siisswasserpolypen. &c.," Wien. Sitx. 

 1860. 



++ Entwicklungsgeschichte des urunm Avmpolvpen ( Hi/dm rii-idix), ls,>->. 



