ZooL.-Voi.. III.] HOLMES— ON SPHAiROMIDS AND DYNAMENE. 297 



and females occur in each of these species, and that they 

 exhibit no marked degree of sexual dimorphism. 



That Dynamene represents the female form of JVcesa is a 

 conclusion that has more in its favor. At least it may be 

 true that some species of Dynamene may have males that 

 would come under the genus JVcesa. Ncesa hidentata and 

 Dynamene Montagui were regarded by Bate and West- 

 wood^ as probably the male and female of the same species. 

 Dr. Stebbing considers it " not improbable that the species 

 named Dynamene rubra and Dynamene viridis by Leach 

 and Camfecopia versicolor by Rathke, may represent the 

 female, and Dynamene Montagui the young male of Ncesa 

 hidentata. . . . No one appears to have ever found 

 the NcBsa form or Dynamene Montagui carrying eggs, and, 

 as they are not at all uncommon, they may therefore be 

 presumed to be of the male sex." The form described 

 and figured by Hesse, however, is certainly not Dynamene 

 rubra or viridis, and it may be added that the specimen 

 figured as the male of this species differs wonderfully from 

 the figure given by Bate and Westwood. Moreover, the 

 form figured as the female differs so markedly from the 

 male that it would require much stronger evidence than 

 Hesse has adduced to convince a reasonably skeptical per- 

 son that the two forms represent the two sexes of the same 

 species. The differences are not confined to the posterior 

 part of the body but extend to the anterior thoracic seg- 

 ments and head. Hesse does not state under what name 

 the female of this species was previously described or 

 whether it had been described at all. While sexual dimor- 

 phism may exist in the forms Hesse describes, it may not 

 unreasonably be doubted whether this writer has connected 

 the male and female of the same species. 



The attempt was made by Hesse to raise the young of 

 Dynamene in order to ascertain whether they would give 

 rise to any specimens of JVcBsa; but, as in the experiment 

 with Sphceroma, the young all died before reaching a stage 



1 A History of the British Sessile-eyed Crustacea, v. 2, I,ond. 1868. 



