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; crocodilians, 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: monotremes (omithoryncus), birds, batrachians, crustaceans.
5. No copulation; exterior fecundation of eggs: fish, echinoderms.
6. Indirect transmission of sperm with or without contact (by the spermatophore): cephalopodes, orthoptera.
7. Hermaphrodism: mollusks, tuniciers, worms.
8. Monagamous reproduction: protozoaires, and certain of the last metazoaires.
One needs many discriminations and exceptions to make this table more precise. It is however, not untrue, although incomplete and lacking nuances, and it permits one to see: that the separation of sexes by well characterized copulating apparatus is not a sign of animal superiority, although it is found among the most gifted animals; that birds with their genital system merely sketched in, seem to represent a type elevated in nature by the simplicity of organs and it means: that the sexes in animals who are without copulation either profound or superficial, tend, as in fish, to remain without difference; that all other modes of copulation are attributed exclusively to inferior species; that hermaphrodism was but a trial limited to a category of creatures lacking everything not exclusively designed for the process of reproduction; that the absence of sex characterizes only the earliest forms of life.