23r, 



THE AMERICAN NATURALIST [Vol. LIV 



variation in the chromosome mechanism. At present we 

 do not know how a parthenogenetic female sometimes 

 produces . female (parthenogenetic) broods, at other 

 times male broods or sexual eggs. That such changes 

 may be brought on by environmental changes seems not 

 improbable from the large amount of data already col- 

 lected. The results in these respects are so similar to 

 those in rotifers where the situation is now under con- 

 trol (Whitney) that one can scarcely resist the convic- 

 tion that in both cases the environment acts in produc- 

 ing the changes. But while we have no explicit evidence, 

 as yet, even in Hydatina, that the environment acts only 

 by bringing about changes in the chromosome mechan- 

 ism, there is at least nothing known opposed to such a 

 view, and some general arguments that incline one to 

 anticipate such a discovery. Until these matters are set 

 straight not much is to be gained by speculating as to 

 how the sex intergrades of Simocephalus and other 

 Daphnia arise. But if it should be found that the nor- 

 mal cycle is caused by alterations in the chromosome 

 cycle, as has been shown in fact for Phylloxerans and 

 Aphids, then I think we may have to look to some aber- 

 rations in the same mechanism to explain these anoma- 

 lous cases. Indeed the kind of inheritance described by 

 Banta appears to be one that might be expected from 

 such a situation. 



In the genus Cyclops, Mrazek (1914) has described 

 ' ' androgynes " that have modifications in the antennae, 

 and Bremer (1914) has recorded two cases of ' 1 pseudo- 

 hermaphrodites " in Diaptomus. 



In sharp contrast to these kinds of intersexes in the 

 lower crustaceans stand out the bilateral gynandro- 

 morphs that have been found in two genera of lobsters. 

 Nichols in 1734 described a lobster whose right side was 

 female and whose left side was male. Dissection showed 

 an ovary in the female side and a testis on the left. A 

 similar case was described for Palinurus in 1902 (Bur- 

 ger), but no dissection was made. 



