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XXIX.— 01^ THE GENEEATIYE AND URINAEY DUCTS IN 

 CHITONS. Bt ALFRED C. HADDON, M.A., M.R.I.A., 

 Professor of Zoology, Eoyal College of Science, Ireland. 

 (Plates X. and XI.) 



[Eead, April 21, 1884.] 



Cfenerative Bucts. — There is as a matter of fact notHng 

 especially remarkable about the generative organs of Chitons. 

 Cuvier (1), Middendorff (2), Yon Jhering (6), &c., describe paired 

 generative ducts arising from the median unpaired generative gland. 

 The oviducts arise, according to Haller (11), in Chiton sicuhis and 

 Ch. fasciciilaris from a dilated and folded uterus, which is situated 

 at about the hinder third of the ovary on the ventral side. Sedg- 

 wick (8) {Ch, discrepans and Ch. cancellatus) does not state whether 

 the ducts arise from the dorsal or the ventral side of the generative 

 organ. Van Bemmelen (12) mentions that the efferent duct in Ch. 

 marmoreus and Ch. marginatus springs from the dorsal side, and my 

 own investigations on various forms agree with the latter statement. 

 The ducts take a more or less direct course to the gill-row, and usu- 

 ally open near the fourth or fifth gill, counting from the posterior 

 end. Hubrecht (10) has confirmed by sections " the presence of the 

 same arrangement in Ch. marginatus.''^ Sedgwick (8) states that 

 " the male duct has a short direct course to its opening ; while the 

 female duct is much coiled." This, at all events, is not the uni- 

 versal case. According to Sedgwick and Haller (11) the duct curls 

 round the upper border of the lateral nerve cord, between it and the 

 gill vein, and thus opens to the exterior, internal to the gill-row. 



Dall in a short Paper, published in 1874 (5), states that in 1869 

 he had noticed the fact that the ovarian openings are not invariably 

 simple apertures. Their position had been previously known, but 

 it is not uniform in all Chitons. In some the fenestrse are close to 

 the anus, and single on each side. In describing the orifices of Ch. 

 ruber (Lin.) he says, "The 'cancellated space,' noticed by Mr.Emer- 

 ton (as per notice in Ann. Mag. Nat. Hist., Mar., 1874), on each 

 side, behind the branchiae, is a fold or groove containing the ova- 



