THE WONDERS OF LIFE 



vagueness in its effect. As a rule, hybrids exhibit a 

 combination of the features of both parents. 



It has been proved by many recent experiments that 

 hybrids have a more powerful build and can repro- 

 duce more strongly than pure offspring, whereas pure 

 selection has generally in time an injurious effect. A 

 freshening by the introduction of new blood seems to be 

 good from time to time. Hence, it is just the reverse of 

 what the former dogma of the constancy of species 

 affirmed. The question of hybridism has, generally 

 speaking, no value in defining the species. Probably 

 many so-called "true species," which have relatively 

 constant features, are really only permanent hybrids. 

 This applies especially to lower sea-dwelling animals, the 

 sexual products of which are poured into the water and 

 swarm together in millions. As we know of various 

 species of fishes, crabs, sea-urchins, and vermalia, that 

 their hybrids are very easily produced and maintained 

 by artificial impregnation, there is nothing to prevent 

 us from believing that such hybrids are also maintained 

 in the natural state. 



The short survey we have made of the manifold 

 varieties of reproduction is sufficient to give an idea of 

 the extraordinary wealth of this world of wonders. When 

 we go more closely into details we find hundreds of other 

 remarkable variations of the process on which the main- 

 tenance of the species depends. But the most im- 

 portant point of all is the fact that all the different 

 forms of tocogony may be regarded as connected links of 

 a chain. The steps of this long ladder extend uninter- 

 ruptedly from the simple cell-division of the protists to 

 the monogony of the histona, and from this to the com- 

 plicated amphigony of the higher organisms. In the 

 simplest case, the cell-cleavage of the monera, prop- 

 agation (by simple transverse division) is clearly noth- 

 ing more than transgressive growth. But even the pre- 



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