BV WILLIAM A. IfASWELL, M.A., B.SC. 259 



and nearly always open internally into the cavity of the body, 

 and the sexual products are developed in the body cavity by a 

 sort of germination of the lining membrane. Moreover I have 

 found in these species of Fohjnoina whose structure I have 

 specially studied segmental organs not markedly different from 

 those of other Annelides, and sexual glands having the normal 

 relations. It will therefore not be inadmissable to suppose that 

 "Williams's representation of these structures must have been 

 founded in some way or other on erroneous inferences. It 

 seems to me most probable that what AVilliams took for the 

 segmental organ was a part of the dorsal branched portion of 

 the intestinal cpeca, and that his ciliated efferent duct was the 

 ciliated neck of communication between the caecum and the 

 intestine. The intimate manner in which the ovaries are related 

 to those ca3ca would help to account for this. When he states 

 positively that the ova are most clearly seen in the interior of 

 the branching tubuli, it is evident that he had misj;aken the 

 yellow cells for young ova ; what he figures as spermatozoa do 

 not at all resemble the spermatozoa of the Fohjnoina which I 

 have studied, and here too there may have been a wrong deduc- 

 tion. Be this as it may, it is perfectly conclusive as shewing 

 that William's descriptions, whatever be their precise explanation, 

 are erroneous, that the fully developed sexual products both in 

 Aplirodita and Pelynoe are found floating freely in the perivisceral 

 fluid, which could not be the case were they formed in the interior 

 of c?ecal tubes opening only on the exterior. 



While there is some difficulty in explaining Williams's state- 

 ments on this subject, Ehlers's description and figure on the 

 other hand are so clear as to leave no doubt at all as to the nature 

 of the error into which he has fallen. In describing the anatomy 

 of Polynoe pellucida he states* : — •' Segmentalorgane habe ich vom 

 zweiten Segmente an in alien vollig ausgebildeten Segmenten 



* L. c, p. 116. 



