Chat, it.] OF ANIMAL GENERATION. 321 



narrow toward the middle, and form thus a couple conducted 

 by the anterior individual.' Finally the separation is effected, 

 and each of the halves completes itself. The najids divide them- 

 selves in the same manner transversally into two parts, of which 



Fio. 46. 



AvuBba spTuerococcus, in the different stages of its evolution. A, encysted amael)a. Proto- 

 plasmic mass (c), containing nucleus (d), nucleole (a), and enveloping membrane (d). S, 

 amoeba freed from the enveloping membrane ; C, amoeba commejiciug to divide iteelf ; 

 Da and J)&> amoeba totally divided into two independent parts. 



the anterior remakes itself into a head, and the posterior into 

 a tail. 



It is by germination or gemmiparity, that is to say, by a 

 variety of fissiparity, that are formed the aggregations, the 

 colonies of the zoantharies. Sometimes the bud detaches itself, 

 playing the part of a vegetal spore or bulbille, and goes to form 

 an independent individual. 



Many monadaries seem to reproduce themselves solely by 

 gemmiparity. This mode of generation exists sometimes alone, 

 sometimes associated with sexuality, sometimes alternating with 

 this last in many inferior animals. In the hydras or fresh-water 

 polypi we easily see the young hydras budding on the mother 

 hydra. Their body at first communicates with the cavity of that 

 of the mother, and is nourished at the expense of the same until 

 the moment when the new iadividual is in its turn furnished with 

 prehensile tentacles capable of seizing its prey. 



■ Dnges, Physiologie Comparie, t. I. p. 213. 



