60 THE EVOLUTION OF SEX. 



CHAPTER VI. 

 HERMAPHRODITISM. 



I. When an organism combines within itself the production of 

 both male and female elements, it is said to be bisexual or hermaph- 

 rodite. This is the case with most flowers, and with many lower 

 animals, — such, for instance, as earthworms and snails. It is not 

 desirable to extend the term, as is sometimes done, to cases like 

 ciliated infusorians, where sex itself is only incipient. Undoubtedly 

 in those Protozoa recent researches have distinguished what in loose 

 analogy may be called male and female nuclear elements, but this 

 primitive condition is rather a state antecedent to sex than a union 

 of sexes in one organism. 



In most phanerogams, as every one knows, male and female 

 organs occur on different leaves (stamens and carpels) of each flower. 

 The flower as a whole, or the entire plant, may then be called her- 

 maphrodite. But as the male and female organs are restricted to 

 different leaves, each leaf by itself unisexual, when compared, for 

 instance, with the prothallus of a fern, which bears on the same small 

 expansion both male and female organs. When stamens and carpels 

 unite together, as in orchids, a more intimate hermaphroditism is 

 obviously developed. So with animals. While the general definition 

 of hermaphroditism, as the union of the two sexes in one organism, 

 is plain enough, the union is exhibited in a great variety of ways and 

 degrees. Of these it is necessary first to take account. 



II. Embryonic Hermaphroditism.— Some animals are her- 

 maphrodite in their young stages, but unisexual in adult life. Allusion 

 has already been made to the case of tadpoles, where the bisexuality 

 of youth occasionally lingers into adult life. According to some, 

 most higher animals pass through a stage of embryonic hermaphro- 

 ditism, but decisive proof of this is wanting. 



The research of Laulanie may now be referred to at greater length. 

 As the result of observation on the development of the reproductive 

 organs in the higher vertebrates, and especially in birds, he seeks to 

 establish a strict parallelism between the individual, and what he 

 believes to have been the racial history. In the chick, he distinguishes 

 three male stages in the development — (i) germiparity, (2) her- 

 maphroditism, (3) differentiated unisexuality. These he regards as 

 recapitulating the great steps of the historic evolution. (1) For 

 the first period of "germiparity,"— from the fourth to the sixth 



