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THE AMEBIC AN NATURALIST [Vol. XLIII 



with a duct leading to a single male opening on the ulti- 

 mate leg. Though no sperm was present it seemed as if 

 sperm might have been made. It appears that this 

 individual could have been of little or no use to the race. 



With this exception all sexually abnormal crayfishes, as 

 far as known, are either males or females with either some 

 duplication of organs that belong to that one sex or else 

 the addition of external organs of the opposite sex. But 

 in Parastacus there is also some duplication of internal 

 ducts, which needs additional investigation to show how 

 far it is duplication and how far it may be the addition 

 of ducts of the other sex. As far as Lonnberg's observa- 

 tions go the extra ducts were like the normal of that sex 

 and not like those of the other sex. 



The fact that the male may have merely the external 

 openings of the female sex without any internal female 

 organs shows that the gonad is not necessary as a stim- 

 ulus for the making of the external organ, that the ex- 

 ternal organ is not correlated with the gonad by any 

 internal secretion or other means, necessarily. At the 

 same time Parastacus shows that when there are extra 

 openings, or rather sham openings, the gonad sends extra 

 ducts towards those openings so that there seems a corre- 

 lation between the gonad and the external organ that 

 belongs to the opposite sex. However, Lonnberg found 

 in some of the testes of Parastacus objects that he thought 

 might be eggs ; so that the purity of the gonads is some- 

 what doubtful. 



There is a possibility that these males may have had 

 enough development of a hermaphrodite gonad to supply 

 a stimulus to the surface that would make the external 

 female organs begin to develop in the right place for a 

 female having ovaries, though the gonad was essentially 

 male. 



The gonads of crayfishes are late in becoming visible 

 in the ontogeny of the individual and the external organs 

 do not show till the eggs have hatched and passed into 

 the third larval stage, after two moults. Whether these 



