Haddon — On Generative and Urinary Ducts in Chitons. 225 



openings near the anus were absent. The specimen was a male. 

 Some of these differences may Tbe sexual : at all events, the subject 

 requires investigation from living specimens." Ch. trifida. — 

 " No ovarian openings could be detected." Ch. australis. — " The 

 ovarian openings situated close on either margin of the anus." 

 Ch. wossnessenskii (Midd.) — "No distinct oviduct could be ob- 

 served." Ch. imporcata (Carp.) — " No oviduct could be traced though 

 the ovary was crowded with eggs." Ch. vestita (Sow.) — "The 'ova- 

 rian' openings, bilaterally symmetrical, are situated just behind 

 and, as it were, under the shadow of the posterior branchia on each 

 side. They are not simple orifices, but fenestrse, composed of two 

 openings somewhat oblique and linear ; the anterior a little nearer 

 the girdle, and a little larger than the posterior one." ChitoneUus 

 fasciatus. — " There seemed to be two oviducts leading from a single 

 ovary to small orifices, one on each side of the anus." In a few 

 other species Dall has identified the normal arrangement stated 

 above at the commencement of this Paper. 



I have recapitulated Ball's statements, in order to show the 

 great difficulty there is in making out certain details of the inter- 

 nal anatomy simply by dissection of spirit-hardened specimens. If 

 it had been possible to sectionize these examples, the relations of the 

 generative ducts would have been elucidated ; and, for the future, 

 it appears to me, we must be cautious in admitting the absence of 

 generative ducts in Chitons till we have microscopical evidence to 

 prove it. 



My own observations on the oviduct of Ch. ruber call for little 

 comment. The duct arises on the dorsal wall of the ovary, near 

 its posterior end, as a dilated, ciliated, or rather flagellated sack, 

 which at first runs parallel to the gland, and then diverges out- 

 wardly, narrowing into a circular oviduct, lined with ciliated cubical 

 cells, and possessing a large lumen. This pursues a straight course 

 outwards, being slightly directed backwards, and ends with tumid 

 folded lips, between the foot and the branchial vein, about the level 

 of second and third gill, counting from behind. 



The general nature of this duct will be seen on reference to 

 figure 1, plate X., which is a camera-lucida drawing combined 

 from one or two consecutive sections, and is not an ideal diagram. 

 The state of preservation prevents me from adding those histo- 

 logical details which I should wish. 



