THE ORIGIN OF GYNANDROMORPHS. 



description of a few of them was published we have continued to keep 

 records of their occurrence. Others, too, working with our mutant 

 types have found them, and a few have been described by Dexter, 

 Duncan, and Hyde. We soon realized that they occurred with suffi- 

 cient frequency to make it possible to devise experiments of a sort to 

 furnish the long-sought criterion as to the most common method of their 

 occurrence. It is this evidence on which we wish now to lay chief 

 emphasis. 



The ordinary gynandromorph is an animal that is male on one side 

 of the body and female on the other. The reproductive organs, 

 gonads, and ducts may or, hi bees at least, may not show a corre- 

 sponding difference. A typical case of a gynandromorph that is 

 bilateral, at least superficially, is represented in plate 1, figure 1. For 

 a long time it has been recognized that bilateral gynandromorphism 

 is only one kind of abnormal distribution of the sex characters; even 

 in the classical case of the Eugster bees (see p. 74) other distributions 

 of the characters were recorded. In the fly represented in plate 3, fig- 

 ure 2, the upper part of the abdomen is female, but the lower side of the 

 abdomen, notably the external genitalia, are male. In the individual 

 represented in plate 3, figure 5, the left anterior side of the head is 

 male, the right fe- 

 male, while the left 

 posterior parts of the 

 body are female, the 

 right male. Other 

 cases will be described 

 later in which even 

 more irregular and 

 complex distributions 

 of male and female 

 parts exist. B 



Before discussing TEXT-FIGURE 1. 



these and other cases 



in detail, it may be well to give three of the most recent interpreta- 

 tions of gynandromorphism resting on a chromosomal basis and the 

 criteria by which the validity of each has been tested. 



In 1888 Boveri suggested that on rare occasions a spermatozoon, 

 on entering the egg, might be delayed in its penetration to the vicinity 

 of the egg-nucleus, and the latter might meanwhile have begun to 

 divide, so that the sperm-nucleus came to unite with only one of its 

 halves. In consequence, two kinds of nuclei would be produced in 

 the embryo (text fig. 1 A). The nuclei that come from the sperm plus 

 the half egg-nucleus would be diploid. If, as in the bee, one nucleus 

 stands for the male and two for the female, it follows in such cases 

 that all those parts of the body whose nuclei are derived from the 



