126 



REPRODUCTION. 



attached to the parent withers away, the animal is detached 

 and becomes independent. Others remain through life 

 attached to the parent stalk, and in this respect, present 

 a more striking analogy to the buds of plants. But in 

 the polyps, as in trees, budding is only an accessary mode 

 of reproduction, which presupposes a trunk already existing, 

 originally the product of ovulation. 



330. Reproduction by division, or fissiparous reproduction, 

 is still more extraordinary ; it takes place only in polyps and 

 some infusoria. A cleft or fission at some part of the body 

 takes place, very slight at first, but constantly increasing in 



depth, so as to become a deep 

 furrow, in the same way as 

 takes place in the yolk, at the 

 beginning of embryonic devel- 

 opment ; at the same time the 

 organs are divided and be- 

 come double, and thus two in- 

 dividuals are formed of one, so similar to each other that 

 it is impossible to say which is the parent and which the 

 offspring. The division takes place sometimes vertically, 

 as for example, in the Vorticella (Fig. 133) and in some 



Fi?. 133. 



Fig. 134. 



Polyps (Fig. 134), and sometimes transversely. In some 

 Infusoria, the Paramecia, for instance, this division occurs 

 as often as three or four times in a day. 



331. In consequence of the same faculty, many animals 

 are able to reproduce various parts of their bodies when 

 accidentally lost. It is well known that crabs and spi- 

 ders, on losing a limb, acquire a new one. The same 



