i8 TEE POPULAR SCIENCE MONTHLY 



eyes, brains, ears, fins and pulsating hearts, blood and blood vessels, but 

 could live only a limited time because no blood circulation was estab- 

 lished at all — in spite of the fact that the heart beat for weeks — or that 

 the circulation, if it was established at all, did not last long. 



What prevented these heterogeneous fish embryos from reaching the 

 adult stage ? The lack of the proper " dominants " ? Scarcely. I suc- 

 ceeded in producing the same type of faulty embryos in the pure breeds 

 of a bony fish (Fundulus heterocUtus) by raising the eggs in 50 c.c. of 

 sea-water to which was added 2 c.c. one one-hundredth per cent. NaCN", 

 The latter substance retards the velocity of oxidations and I obtained 

 embryos which were in all details identical with the embryos produced 

 by crossing the eggs of the same fish with the sperm of remote teleosts, 

 e. g., Ctenolabrus or Menidia. These embryos, which lived about a 

 month, showed the peculiarity of possessing a beating heart and blood, 

 but no circulation. This suggests the idea that heterogeneous embryos 

 show a lack of " adaptation " and durability for the reason that in con- 

 sequence of the chemical difference between heterogeneous sperm and 

 egg the chemical processes in the fertilized egg are abnormal. 



The possibility of hybridization goes much further than we have 

 thus far assumed. We can cause the eggs of echinoderms to develop 

 with the sperm of very distant forms, even mollusks and worms (Kupel- 

 wieser) ; but such hybridizations never lead to the formation of durable 

 organisms. ^ ' 



It is, therefore, no exaggeration to state that the number of species 

 existing to-day is only an infinitely small fraction of those which can 

 and possibly occasionally do originate, but which escape our notice be- 

 cause they can not live and reproduce. Only that limited fraction of 

 species can exist which possesses no coarse disharmonies in its auto- 

 matic mechanism of preservation and reproduction. Disharmonies and 

 faulty attempts in nature are the rule, the harmonically developed sys- 

 tems the rare exception. But since we only perceive the latter we gain 

 the erroneous impression that the " adaptation of the parts to the plan 

 of the whole " is a general and specific characteristic of animate nature, 

 whereby the latter differs from inanimate nature. 



If the structure and the mechanism of the atoms were known to us 

 we should probably also get an insight into a world of wonderful har- 

 monies and apparent adaptations of the parts to the whole. But in this 

 case we should quickly understand that the chemical elements are only 

 the few durable systems among a large number of possible but not 

 durable combinations. Nobody doubts that the durable chemical ele- 

 ments are only a product of blind forces. There is no reason for con- 

 ceiving otherwise the durable systems in living nature. 



