GEMMIPAROUS ANIMALS. 425 



falling off, upon maturity, to the enjoyment of independent 

 existence. The gemmiparous mode of reproduction is very 

 strikingly exemplified in the genus Hydra, or Fresh-water 

 Polypus. The rudiment of the future young polypus ap- 

 pears as a small tubercle, produced by an elevation of the 

 skin of the parent ; afterwards it projects still farther, and 

 acquires an opening for its mouth and the tentacula sur- 

 rounding its margin ; a natural separation then takes place 

 between the lower part of the young animal and the skin 

 of the parent, when it becomes detached and independent. 

 Two or more such buds may be observed expanding on 

 the same parent at once ; and, previous to the young drop- 

 ping off, other buds may be observed evolving on their 

 surface. 



This mode of reproduction appears to be confined to the 

 class of Zoophytes. It is not, however, the only method 

 of generation exhibited by these animals. The Sertularia? 

 not only increase by the lateral evolution of their young, 

 but by the production of vesicles containing ova. 



As nearly related to the gemmiparous mode of reproduc- 

 tion, we may here take notice of the multiplication of ani- 

 mals by the Spontaneous Division of their bodies. The 

 celebrated ELLIS, in consequence of a hint he received from 

 M. DE SAUSSURE, examined several species of the ani- 

 malcula infutoria, in which he observed the body begin 

 to contract in the middle, and at length to become divided 

 by a transverse separation. Each of the parts assumed an 

 independent existence*. The celebrated MULLER like- 

 wise observed this singular multiplication of individuals 

 taking place both transversely and longitudinally -f. A si- 



Phil. Trans. 1769, p. 138. 



f- Animalcula infusoria, fluviatilia ct marina, quae detexit, systematico 

 descripsit et ad vivum delineari curavit, 0. F. MULLEK. Havnise 1786, 

 praef. p. ix. 



