332 EVOLUTION AND GENETICS 



Hermaphrodites are individuals which bear functional gonads 

 of both sexes, and produce both male and female gametes. It 

 does not follow that they are capable of self-fertilization, although 

 this is sometimes a possibility and sometimes apparently the 

 normal method of reproduction. Hermaphroditism is common 

 among the lower phyla. Sponges and coelenterates, flatworms 

 and annelids include many striking examples. 



Since the individual can have only one chromosome complex, 

 the occurrence of these bisexual forms is absolute proof that 

 chromosomal difference is not an essential of sex. The same 

 processes that produce the gametes in different individuals produce 

 them here in one, and the same result of recombination of parental 

 characters is attained as when the sexes are separate. 



Abnormalities of many kinds occur in nature or can be pro- 

 duced by artificial means which further substantiate this view. 

 Wherever they occur in nature they are apparently due to accidents 

 of development or to abnormal behaviour of the germ cells. 

 Experimentally they have been produced by operative methods 

 and by variation of the environment. 



Gynandromorphs, sometimes incorrectly called hermaphrodites, 

 are occasionally produced among insects of various orders and 

 among other animals. They are individuals which display the 

 characters of both male and female in different parts of the body, 

 and are incapable of carrying on the normal reproductive functions 

 of either sex. 



Gynandromorphs are usually bilateral, one half being male and 

 the other female. In species with distinctly different sexes this 

 results in very striking contrasts as shown in Figure 189. This 

 distribution of sex characters is accompanied ])y a similar asym- 

 metry of chromosome distribution, the female half having the 

 female complex and the male half the male complex. How such 

 an abnormality occurs it is difficult to determine but one logical 

 explanation is available. 



According to this interpretation the first cleavage of the ovum 

 may be hastened by some force so that two groups of chromosomes 

 are present at the consummation of fertilization. The union of 

 the male pronucleus with one of the female pronuclei would 

 establish the diploid complex in one half of the individual while 

 the other half would have only the maternal haploid complex. 

 The diploid complex might readily contain two allosomes and so 



