Cottus cognatus, &c. with Cottus gobio. 125 
importance in settling a question of identity in species, since it 
presents characters much less likely to prove variable than 
those which are merely external. 
The liver is large and rounded; it occupies the whole 
breadth of the abdomen, and in a fish of the size described 
(two inches and six-tenths) is three tenths of an inch in length. 
It is light yellowish red in color, entire, showing but one lobe ; 
the greater part of it lies on the left side. 
The stomach is large and rounded ; the «esophagus enters it 
near its extremity on the left, the pylorus is situated at the 
opposite end. The ceca are four, oblong, blunt, and rounded, 
placed around the intestine close to the pylorus; the longest, 
in a fish of two inches and six-tenths, is two-tenths of an inch 
iù length. The intestinal canal, which is narrow, runs back 
a little distance, turns forward and passes almost to the 
pylorus, and then turning again runs nearly straight to the 
The ovaries are two, elongated, rounded in front, tapering 
posteriorly. Before their termination they apparently unite 
and become one. Still I think the excretory duct is not 
single, but double. As to this, however, I have not been 
able to satisfy myself entirely ; if the duct is double the two 
branches are very closely connected. The membrane sur- 
rounding the ovaries is dotted with black. The organs of the 
male are somewhat similar in form to the ovaries of the female, 
but are more angular in front. They are much lighter in 
color, being almost white, and do not unite into one but con- 
Unue separate throughout their whole length. The seminifer- 
ous ducts are very apparent, and pass back perfectly distinct 
from each other, opening posterior to the anus. = 
The kidneys extend more than half the length of the abdo- 
ae No traces of a urinary bladder can be discerned. A 
Urniferous duct passes back on each side; as it descends to 
"5 termination it is posterior to the one from the generative 
organs but opens, I think, at the same place with it. The 
