STRUCTURE AND DEVELOPMENT OF LEPIDOSTEUS. 
421 
glomerulus is identical in structure with a malpighian body. The ciliated canal is 
similar in its relations to the peritoneal canal of such a segmental tube, and the 
coiled portion of the pronephros resembles the secreting part of the ordinary 
segmental tube. This comparison is no doubt an indication that the pronephros 
is physiologically very similar to the mesonephros, and so far justifies Sedgwick’s* 
comparison between the two, but it does not appear to us to justify the morphological 
conclusions at which he has arrived, or to necessitate any modification in the views on 
this subject expressed by one of us.t 
The genital ducts of Ganoids and Teleostei have for some time been a source of 
great difficulty to morphologists ; and any contributions with reference to the ontogeny 
of these structures are of interest. 
The essential point which we have made out is that the anterior part of the 
oviduct of Lepidosteus arises by a fold of the peritoneum attaching itself to the free 
edge of the genital ridge. We have not, unfortunately, had specimens old enough to 
decide how the posterior part of the oviduct is formed; and although in the absence 
of such stages it would be rash in the extreme to speak with confidence as to the 
nature of this part of the duct, it may be well to consider the possibilities of the case 
in relation to other Ganoids and Teleostei. 
The simplest supposition would be that the posterior part of the genital duct had 
the same origin as the anterior, i.e., that it was formed for its whole length by the 
concrescence of a peritoneal fold with the genital ridge, and that the duct so formed 
opened into the segmental duct. 
The other possible supposition is that a true Mullerian duct— i.e., a product of the 
splitting of the segmental duct—is subsequently developed, and that the open end of 
this duct coalesces with the duct which has already began to be formed in our oldest 
larva. 
In attempting to estimate the relative probability of these two views, one important 
element is the relation of the oviducts of Lepidosteus to those of other Ganoids. 
In all other Ganoids (vide Hybtl, No. 11) there are stated to be genital ducts in 
both sexes which are provided at their anterior extremities with a funnel-shaped mouth 
open to the abdominal cavity. At first sight, therefore, it might be supposed that they 
had no morphological relationship with the oviducts of Lepidosteus, but, apart from the 
presence of a funnel-shaped mouth, the oviducts of Lepidosteus are very similar to those 
of Chondrostean Ganoids, being thin-walled tubes opening on a projecting papilla into 
the dilated kidney ducts (horns of the urinary bladder, Hyrtl). These relations seem 
to prove beyond a doubt that the oviduct of Lepidosteus is for its major part homologous 
with the genital ducts of other Ganoids. 
* Sedgwick, “ Early Development of the Wolffian Duct and anterior Wolffian Tubules in the Chick ; 
with some Remarks on the Vertebrate Excretory System.” Quart. Joui*. of Micros. Science, vol. xxi., 
1881. 
f F, M, Balfour, ‘ Comparative Embryology,’ vol. ii., pp. 600-603, 
