6 DUBLLiN 



observers could have erred regarding the true condition of a 

 character so obvious in mature individuals of all of the Endo- 

 procta. It is more probable that in the disputed cases there is 

 true hermaphroditism disguised by proterandry or proterogyny. 

 Thus Ehlers, '90, suggests the possibility that, " in verschiedenen 

 Jahreszeiten, die Stocke etwa ungleich sexuirte Nahrthiere 

 erzeugten, so dass, zu der einen Zeit, gonochoristische (dioe- 

 cious), zu einer anderen Zeit, hermaphroditische Kelche vorhan- 

 den sind." In like manner, Nickerson, '01, points out that 

 " several periods of sexual activity, alternately male and female, 

 may occur in the same animal." 



These explanations, if accepted, would add to the already 

 large number of cases of true hermaphroditism. For if an indi- 

 vidual, at one time male, can at a later period become female, 

 then it must be clear that the germ-cells of the two sexes really 

 occur side by side in the same polypide, but the height of the 

 developmental period of the two does not occur at the same 

 time. This would make it very probable that hermaphroditism 

 is the primitive condition among the Endoprocta from which, 

 the several exceptions have to a greater or less extent diverged. 



It is this hypothesis which will be applied as an explanation 

 of the peculiar conditions observed in Pedicellina americana. 

 This species may be considered as hermaphrodite, but both 

 sexes do not develop at the same time, nor in the same indi- 

 vidual of the colony. There is in the very young primary poly- 

 pide a mosaic condition of the germ-cells, /. e., there are both 

 primary ^^^ and sperm-cells present side by side. In the proc- 

 ess of growth, only one portion of these develops into a mature 

 ovary or testis, the other remaining indistinguishable as a few 

 primary germ-cells among the other embryonic cells of the 

 body. With the budding, which now ensues, these are carried 

 into the newly formed individual with some of the primary cells 

 of the other sex ; but here, these may, in response to some 

 change in the local conditions, become active and the others 

 latent thus giving rise to a sex opposite to that of the preceding 

 individual. This process may, however, occur for the first 

 time, in the second or in some later budding in the life history 

 of the colony or, in some cases, not at all. 



