THE ORIGIN OF GYNANDROMORPHS. 



97 



characters of the opposite sex. The condition is a very rare one and 

 is usually shown in the external organs only." 



In the Philosophical Transactions for 1734 is a full account of a 

 bilateral gynandromorph lobster by Dr. F. Nichols. The drawings 

 of the external parts show that the animal is female on the right side 

 and male on the left. Dissection showed an ovary with eggs on the 

 right side, and a testis with vas deferens on the left. This case is 

 exactly like the bilateral gynandromorphs of Drosophila, and is the 

 only case known to us of a strictly bilateral type of gynandromorph 

 in the group Crustacea. 



Olga Kuttner (1909) found a wild individual of Daphnia pulex that 

 had some male characters on one side but had two ovaries. Twelve 

 broods were produced and in nearly every brood some individuals were 

 mixed gynandromorphs, but nearly all were predominantly female. 



A similar case has been recorded by Banta for Simocephalus vetulus, 

 (1916). In a pedigreed strain there " suddenly 

 appeared" a large number of "sex intergrades 

 males with one or more female secondary sex 

 characters, females with one to several male 

 characters, and some hermaphrodites with vari- 

 ous combinations of male and female secondary 

 sex characters." The more extreme intersex 

 individuals fail to propagate; others, less modi- 

 fied, reproduce. By propagating from female 

 intergrades mixed broods of males, females, and 

 intergrades are obtained. The noteworthy 

 point here is that the intergrades are mosaics 

 rather than blended forms of the two sexes. 



GYNANDROMORPHS IN MOLLUSCS. 



The molluscs, like the Crustacea, contain a number of hermaphro- 

 ditic species, but there are also species with separate sexes. Here, 

 too, cytological study has failed as yet to demonstrate sex chromo- 

 somes. One species of Crepidula is male in the juvenile state and 

 female in older individuals, at least when certain external conditions 

 are fulfilled. Gould has recently shown that when young males are 

 placed in the vicinity of large females the males absorb their testes 

 and genitalia (ducts and penis) and develop ovaries and oviducts. 

 This case recalls in many ways the conditions in Bonellia as described 

 by Baltzer. If the embryos of Bonellia are isolated they become sexual 

 females without showing the male stage. If, however, the embryo, 

 when ready to settle down, comes to rest on the proboscis of a female 

 it develops into a rudimentary male. A few embryos in cultures may 

 show intermediate or rather hermaphroditic conditions. The cirri- 

 peds referred to above appear, according to one interpretation, suscep- 



oviduct 



testis 

 -/---vas.def 



TEXT-FIGURE 69. 



