STRUCTURE AND DEVELOPMENT OP LEPIDOSTEUS. 
413 
centims. in length. They have the form of simple sacs, filled with ova, and attached 
about their middle to their generative duct, and continued both backwards and for¬ 
wards from their attachment into a blind process. 
With reference to these sacs Muller, has pointed out—and the importance of this 
observation will become apparent when we deal with the development—that the ova 
are formed in the thickness of the inner wall of the sac. We hope to show that the 
inner wall of the sac is alone equivalent to the genital ridge of, for instance, the ovary 
of Scyllium. The outer aspect of this wall— i.e., that turned towards the interior of 
the sac—is equivalent to the outer aspect of the Elasmobranch genital ridge, on 
which alone the ova are developed.'* The sac into which the ova fall is, as we shall 
show in the embryological section, a special section of the body-cavity shut off from 
the remainder, and the dehiscence of the ova into this cavity is equivalent to their 
discharge into the body cavity in other forms. 
The oviduct (Plate 26, fig. 60, ocl.) is a thin-walled duct of about 21 centims. in 
length in the example we are describing, continuous in front with the ovarian sac, 
and gradually tapering behind, till it ends {od'.) by opening into the dilated terminal 
section of the kidney duct on the inner side, a short distance before the latter unites 
with its fellow. It is throughout closely attached to the ureter and placed on its 
inner, and to some extent on its ventral, aspect. The hindermost part of the oviduct 
which runs beside the enlarged portion of the kidney duct—that portion called by 
TIyrtl the horn of the urinary bladder—is so completely enveloped by the wall of the 
horn of the urinary bladder as to appear like a projection into the lumen of the latter 
structure, and the somewhat peculiar appearance which it presents in Hyrtl’s figure 
is due to this fact. In our examples the oviduct was provided with a simple opening 
into the kidney duct, on a slight papilla ; the peculiar dilatations and processes of the 
terminal parts of the oviduct, which have been described by Hyrtl, not being present. 
The results we have arrived at with reference to the male organs are very different 
indeed from those of our predecessor, in that we find the testicular products to be 
carried off by a series of rasa efferentia , which traverse the mesorchium, and are con¬ 
tinuous with the uriniferous tubuli; so that the semen passes through the uriniferous 
tubuh 'into the hidney duct and so to the exterior. IE e have moreover been unable to 
find in the male a duct homologous with the oviduct of the female. 
This mode of transportation outwards of the semen has not hitherto been known to 
occur in Ganoids, though found in all Elasmobranchii, Amphibia, and Amniota. It 
is not, however, impossible that it exists in other Ganoids, but has hitherto been 
overlooked. 
Our male example of Lepiclosteus was about 60 centims. in length, and was no 
doubt mature. It was smaller than any of our female examples, but this according to 
Garman (vide, p. 361) is usual. The testes (Plate 26, fig. 58 A, t.) occupied a similar 
position to the ovaries, and were about 21 centims. long. They were, as is frequently 
* ‘ Treatise on Comparative Embryology,’ vol. i., p. 43. 
