THE NATURAL 



also to be studied separately. Finally, the amorous 

 habits of insects form a series of illustrative chapters. 

 From here, taking count only of exterior male organs 

 or of organs which, internal when at rest, emerge at 

 the moment of coition, one may attempt a vague and 

 new classification of animal series. 



1. Presence of penis, or of an erectile copulating 

 tubercle: placentary mammals from man to marsupials 

 exclusively; certain runners and palmipedes; crocodil- 

 ians, chelonians, certain selacians, arthropodes, the 

 rotifera. 



2. Presence of a forked penis: marsupials, saurians, 

 chelonians; scorpionides. 



3. Disjunction of the secreting apparatus from the 

 copulating apparatus: spiders, dragon-flies. 



4. Absence of penis, copulation by contact: mono- 

 tremes (ornithoryncus), birds, batrachians, crustaceans. 



5. No copulation; exterior fecundation of eggs: fish, 

 echinoderms. 



6. Indirect transmission of sperm with or without con- 

 tact (by the spermatophore) : cephalopodes, orthoptera. 



7. Hermaphrodism: mollusks, tuniciers, worms. 



8. Monagamous reproduction: protozoaires, and cer- 

 tain of the last metazoaires. 



One needs many discriminations and exceptions to make 

 this table more precise. It is however, not untrue, al- 

 though incomplete and lacking nuances, and it permits 

 one to see: that the separation of sexes by well char- 

 acterized copulating apparatus is not a sign of animal 

 supeiiority, although it is found among the most gifted 

 animals; that birds with their genital system merely 

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