THE WONDER.S OF LIFE 



plucked may, if put in water, keep fresh and alive for 

 many days. In some highly organized cephalopods one 

 of the eight arms of the male develops into an inde- 

 pendent body, swims about, and accomplishes the 

 fertilization of the female (hectocotylus among the 

 argonauta, philonexis, etc.). It was at first thought to 

 be an independent animal parasite. The same thing 

 happens with the remarkable foldlike dorsal append- 

 ages of a large naked snail (thetys), which get detached 

 and creep about. The body of many of the lower 

 animals may be cut in pieces and yet may live for weeks. 

 The life-properties of these partial bionta are important 

 in view of the general question of the nature of life and 

 its apparent unity in most of the higher organisms. As a 

 fact, even here the cells and organs lead their separate 

 individual life, though they are subordinate to and 

 dependent on the whole. 



It has been attempted to answer this question of 

 organic individuality in the sense of counting all or- 

 ganisms individuals which develop from a single fer- 

 tilized ovum. Thus, the Italian botanist Gallesio, in 

 1816, regarded all plants that arise by asexual generation 

 (budding or segmentation) — sprouts, branches, slips, 

 bulbs, etc. — as merely portions of a single individual 

 that came from an egg (the seed). So also Huxley, in 

 1855, considered the sum of all the animals that have 

 been produced by asexual propagation, but from a single 

 sexually generated animal, to be parts of one individual. 

 In practice, however, this principle is useless. We 

 should have to say that the millions of plant-lice which 

 arise parthenogenetically from unfertilized germ-cells, 

 but are originally descended from one impregnated 

 ovum, are one single individual ; so also all the weeping- 

 willows in Europe, because they all came from shoots of 

 one single sexually-produced tree. 



Many attempts have been made in the course of the 



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