202 



BtrtLETlN OP THE BXJREAU OK FISHERIES. 



ov. Z. 



There is this difference between the oviducal membrane of the smelt and the funnel 

 of the ganoids mentioned, that in the Smelt the membrane turns outward to become 

 attached to the abdominal wall (fig. 8 g), while in the other form it folds inward and is 

 attached to the mesovarial membrane (fig. ii). In the latter a funnel is formed; in 

 the former, only a half- funnel, which is not a homologue of the ganoidean funnels, but 

 is homologous with the oviducts of other Isospondyli, even (some at least) of those with 



closed oviducts. Any phylogenetic significance 

 of the smelt oviduct then would appear to per- 

 tain only to teleosts and to have no relation to 

 the ganoids. 



The Isospondyli comprise forms which are 

 stated to have closed ovaries and true oviducts 

 as well as those which have free ovaries with 

 funnel-like oviducts or only vestigial oviducts. 

 Besides the previously mentioned species, 

 specimens of Pmnolobus pseudoharengus , P. 

 mediocris, Dorosoma ccpcdianwm, and Hyodon 

 iergisus have been carefully examined. The 

 following two examples will serve to show that 

 the Isospondyli, other than Salmonidse, as rep- 

 resented by the specimens examined, are not 

 radically different in their general structure 

 from the vSalmonidae, but considerably differ- 

 ent from other orders having closed ovaries. 



The clupeoids are supposed to have closed 

 ovaries and oviducts. In the alewife (Pomolo- 

 bus pseudoharengus) , the ovary of a large adult, 

 taken July 4, therefore some time after the 

 breeding season, is long and narrow, extending 

 well back in the abdominal cavity. The mes- 

 ovarium is narrow, the ovary lying close to the 

 air bladder. Anteriorly the line of attachment 

 of the outer edge of the enveloping membrane 

 is close to the junction of the inner attachment 

 of the mesovarium to the ovary, along the outer 

 side of the air bladder, and there is a pro- 

 jection forward of the ovary, which is com- 

 pletely inclosed in membrane with no air-bladder attachment of the mesovarium. 

 Posteriorly the lines of attachment diverge slightly, so that the inner line continues 

 along the air bladder, but the outer one becomes attached nearer to the lateral abdom- 

 inal wall at the side of the air bladder. The mesovarium is so narrow that it is scarcely 

 perceptible except as a fold lying in the outside of the ovary, but the membranous 

 attachment is wider and free from ovigerous lamina;, leaving a noticeable space of free 

 eggs; that is, without otlier covering than the peritoneum of the air bladder. This 

 free-ova portion constitutes the beginning of the oviduct within and on one side of the 

 ovarv. The remainder of the oviduct consists of the extension of the meso^'arium and 



od.a. 



Fig. II. — Left ovary and oviduct of bowfin (Amiatus caJ- 

 TTi^), after Huxley. X643. or. /.. left ovary; m.o./., left 

 mesovarium; od. /.. left oviduct; od. a., opening of ovi- 

 duct into the bladder. 



