74 ZOOPHYTES. 



older authors — is a simple animal, uncombined with any other organic 

 structure, and which, on dissection, has shown but little to the anatomist ; 

 and that its form is permanent from the origin to the close of its exist- 

 ence. 



On the other hand, in some instances, the hydra of zoophytes in 

 maturity is simple ; it is almost always, if not uniformly so in the nascent 

 state of others. In adult zoophytes, the majority of hydrse are combined 

 with a simple inorganic structure, often that which is complex, a cell or a 

 stem, or a boundless multitude of branches and terminal cells, with their 

 tenants all enjoying an independent condition or reciprocally connected 

 together. In some this connection is obvious; in some obscure; and 

 masses of thousands of pinnate hydrse comprise the living animals, scarcely 

 separated by a fleshy partition in the carnose tribes. 



There are three hydrse in Scotland which I consider strictly of the 

 individual nature of the hydra proper — namely the Hydra viridis and the 

 Hydra fusca of the Systema — both inhabitants of the fresh waters; — and 

 the Hydra gelatinosa, strobila, or tuba, of the sea, which appear synony- 

 jyious : — as hydrce all exhibit common properties. The body consists of a 

 variable sac, having a dilateable orifice environed by tentacula, endowed with 

 an adhesive and a prehensile faculty. The whole are highly carnivorous ; 

 they propagate the young in their own likeness, by gemmation or budding 

 from the side ; they regenerate mutilated parts : and adults, as well as 

 young, if cut asunder, become entire animals. 



Being hardy by nature, easily fed, preserved, and subjected to experi- 

 ment, they are peculiarly adapted for minute and protracted study. Their 

 accessibility, their size, and tenacity of life besides, wherein they surpass 

 most of the zoophytical tribes, render them favourable objects for observa- 

 tion ; because the delicacy and minuteness of many others, not omitting the 

 higher organization of a number, truly removing them from the genus 

 Hydra, deny the same facilities to the naturalist. 



When the fresh-water polypus became better known, before the 

 middle of the preceding century, its singular properties aroused the admira- 

 tion of those who devoted themselves to the investigations of Nature. To 

 behold a living animal perpetuate its race, by simple gemmation from the 



