INSTANCES OF HERMAPHRODITISM IN CRAYFISHES 
By WILLIAM PERRY HAY 
Howarp UNIVERSITY, WASHINGTON, D. C. 
Hermaphroditism, that condition in which both sexes are com- 
bined in the same individual, is an interesting deviation from the 
normal line of animal development and as it affects not only the 
organs of reproduction but extends its effects to all the secondary 
sexual characters as well, it is worthy of the biologist’s attention. 
Among certain of the lower animals the hermaphroditic condition 
seems to be the normal one just as in the great number of flowering 
plants the normal condition is to have both pistil and stamens’ 
developed in the same flower, but in the case of these animals as 
in the flowers mentioned there is usually some device by which self 
fertilization is prevented or made very difficult. Among those ani- 
mals and plants in which distinct sexes have been developed herma- 
phroditism is very rare. In animals there is a period during which 
the embryo is non-sexual but its subsequent development is almost 
invariably along either the male or the female line. 
In the case of the decapod Crustacea the only instance of un- 
doubted hermaphroditism recorded is that of the lobster, Homarus 
vulgaris, described and figured by F. Nicholls in 1730.1. The spec- 
imen externally showed the male sexual organs on the left side 
and the female organs on the right side. On being dissected the 
internal sexual organs were found to correspond; the right half of 
the body, therefore, was normally female while the left half was 
normally male. 
Coming now to the crayfishes, the first recorded instances of 
abnormal development of sexual characters are by Rosseau and 
Desmarest.* In these cases females of Astacus fluviatilis were 
observed to possess two pairs of sexual orifices, one on the third, 
the other on the fourth pair of legs, which led by a branched oviduct 
to the ovary on each side of the body. 
In 1870 Von Martens described three specimens of an Australian 
* Philosophical Transactions of the Royal Society of London, vol. xxxvt, 
No. 413, p. 290. 
* Annales de la Societe Entomologique de France, 2d Series, vi, pp. 479 and 
481, pl. x11, 1848. 
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