14:98 THE STORY OF THE UNIVERSE 



deeply divided corolla, so that the hive-bees should 

 be enabled to suck its flowers. Thus I can under- 

 stand how a flower and a bee might slowly become, 

 either simultaneously or one after the other, modified 

 and adapted to each other in the most perfect man- 

 ner, by the continued preservation of all the indi- 

 viduals which presented slight deviations of struc- 

 ture mutually favorable to each other. 



I must here introduce a short digression. In the 

 case of animals and plants with separated sexes, it is 

 of course obvious that two individuals must always 

 (with the exception of the curious and not well un- 

 derstood cases of parthenogenesis) unite for each 

 birth; but in the case of hermaphrodites this is 

 far from obvious. Nevertheless there is reason to be- 

 lieve that with all hermaphrodites two individuals, 

 either occasionally or habitually, concur for the re- 

 production of their kind. This view was long ago 

 doubtfully suggested by Sprengel, Knight, and K61- 

 reuter. We shall presently see its importance; but I 

 must here treat the subject with extreme brevity, 

 though I have the materials prepared for an ample 

 discussion. All vertebrate animals, all insects, and 

 some other large groups of animals, pair for each 

 birth. Modern research has much diminished the 

 number of supposed hermaphrodites; and of real 

 hermaphrodites a large number pair; that is, two 

 individuals regularly unite for reproduction, which 

 is all that concerns us. But still there are many her- 

 maphrodite animals which certainly do not habitu- 

 ally pair, and a vast majority of plants are hermaph- 

 rodites. What reason, it may be asked, is there 



