GEMMIPAROUS ANIMALS. 495 
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 Sertulariz 
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 Exuis, in consequence of a hint he received from 
M. De Saussure, examined several species of the ani- 
malcula infusoria, 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 Mutier like- 
wise observed this singular multiplication of individuals 
taking place both transversely and longitudinally +. A si- 

* Phil. Trans. 1769, p. 138. 
+ Animalcula infusoria, fluviatilia et marina, que detexit, systematice 
descripsit et ad vivum delineari curavit,O. F. Munurr. Havnie 1786, 
preef. p. ix. 
