Biology 



The difficulties, inherent in large size are felt by life in all 

 its forms; as a matter of fact the evolution of higher from lower 

 forms abounds in devices for overcoming these difficulties. 



The lowest forms of life, however, have never seriously faced 

 the problem. As soon as the inconveniences of growth are felt, 

 they are surmounted by the simple process of division into two 

 halves, or, as it is technically called, of binary fission. Bacteria, 

 unicellular animals and plants, and the cells of which the bodies 

 of higher, multicellular organisms are built, multiply almost with- 

 out exception by this method. 



It will be seen that sex does not enter into this simplest and 

 most obvious method of reproduction; furthermore, no substance 

 is lost in the process; the one whole simply divides into halves, 

 which then are reorganised into two new wholes. 



Fission continues as a common method of reproduction 

 among the simpler types of multicellular animals. Many worms, 

 for instance, adopt it; in some cases the products of division may 

 remain attached, forming a chain for some time. (See figure 

 facing p. 685.) 



But as Evolution proceeds, fission becomes more and more 

 difficult. In an insect, for instance, or a cuttlefish, the processes 

 of reorganisation after division would be impossibly complicated ; 

 and, while division and reorganisation were going on, the animal's 

 powers of movement would be interfered with, and it would fall 

 an easy victim to its enemies. 



When the organism becomes more complicated, therefore, 

 other methods have to be devised. The commonest method, which 

 prevails in corals and many other Coelenterates, in some worms, 

 and in the degenerate relatives of the vertebrates known as Ascid- 

 ians, is that of budding. 



Budding is in essence unequal fission. The organism as a 

 whole remains unaltered, except that one small portion of it is 

 divided off and becomes reorganised into a new miniature whole. 

 Usually the bud remains attached to the parent during its period 



