368 



Experimental Zoology 



Quetelet found 133.5 males to 100 females; Bodio gives: — 



Males 



Italy . 



France 



Germany 



Austria 



Hungary 



Switzerland 



Belgium 



Holland 



Sweden 



NonA^ay 



Denmark 



131. 1 

 142.2 

 1283 

 132. 1 

 130.0 



135-0 

 132.0 

 127,1 

 1350 

 124.6 

 132.0 J 



■ to 100 females 



From these results it is clear that the proportion of male to 

 female embryos is distinctly in favor of the males. The mean- 

 ing of this is unknown. 



Monoecious Species, composed of Bisexual or Hermaphrodite 



Individuals 



Since the groups of animals with which we are most famihar, 

 the vertebrates, insects, and higher crustaceans, are composed 

 of individuals with separate sexes, we are apt to forget how often 

 in other groups the sexes, or more accurately the sex-cells, are 

 united in the same individual. In the following list some 

 of the groups are given in w^hich hermaphrodite individuals 

 exist : — 



Sponges, sexes separate or united. 



Coelente rates, sexes separate or united, 



Flatworms, sexes united, a few cases of separate sexes. 



Nemerteans, sexes rarely united. Separate sexes the rule. 



Nematodes, sexes separate as a rule, hut united in some cases. 



Annelids, ssxes united in earthworms, separate in marine worms (except 



Protodrilus). 

 Crustacea, sexes separate, but united in some barnacles. 

 MoUusca, sexes separate in some, united in other groups. 

 Echinoderms, sexes separate, united in a few cases. 



Thus in the greater number of the great groups, hermaphro- 



