276 THE COURTSHIP OF ANIMALS 



tissues^ : the patterns and the sculpture of the shell 

 depending on the manner of growth." Just so : and 

 this is surely the fundamental explanation of ornament, 

 using this term in its widest sense, everywhere in the 

 Animal Kingdom. The peculiarities and eccentricities 

 of behaviour, which occur among the higher groups, act 

 as " aphrodisiacs " to hasten reproduction because this 

 confers an advantage, the earliest to produce offspring — 

 so soon as the conditions for their nurture are favourable 

 — having the best chance of survival. Premature sexual 

 activity is checked by the death of the offspring. 



It has been contended that the hermaphrodite con- 

 dition represents the primitive mode of reproduction 

 among the multicellular animals — that is to say, all 

 animals above the level of those whose bodies are com- 

 posed of but a single cell, or particle, of protoplasm— 

 but this view is probably erroneous, and the herma 

 phrodite state must be regarded as a secondary condition, 

 a later innovation. 



More remarkable are the facts concerned with that 

 singular form of reproduction known as parthenogenesis, 

 or the production of offspring by virgin females. This 

 is undoubtedly a degenerate sexual condition occurring 

 as a normal mode of reproduction, among the microscopic 

 " Rotifers," e.g., the " Wheel-animalcule," Crustacea, 

 and Insects, and in varying degrees of intensity. 



The most familiar instances of Parthenogenesis are 

 furnished by the Hymenoptera, and notably by the Bees 

 and the Aphides. 



There are certain cases among the Rotifers where no 

 males have ever been found, and it is possible that they 



* Italics mine. 



