III. COTTOIDS OF NORTH AMERICA. 31 
7 
§ 10. THe ALIMENTARY CANAL, URINARY BLADDER, AND OVARIES, IN Corromns. 
Knowing the animal diet of Cottoids, we may expect a narrow and short aliment- 
ary canal. Its entire length from the pylorus to its posterior opening does not 
exceed the length of the trunk, the head and caudal fin excluded. 
On exposing the splanchnic organs by the removal of the walls of the abdominal 
cavity, from below, the liver is seen occupying the anterior and left portion of that 
cavity, covering completely the stomach, whilst the right portion is occupied by 
the winding of the intestine. Posteriorly are the ovaries, a right and a left, which 
when containing eggs fill up the cavity in that region, leaving a narrow passage to 
the intestine along the medial line of the belly. 
In Cottus viscosus the general form of the stomach is subcircular, or rather 
elliptical. The cardia is proportionally prominent and directed forwards, at the 
termination of which, and around the pylorus, are four elongated, pyloric, nearly 
equal appendages. Here the intestine runs backwards, then forwards again, and 
finally takes a straight course towards the vent, thus bending twice upon itself. 
Its anterior half is much broader than the posterior one. 
In Acanthocottus virginianus and Triglopsis Thompsonii it differs but little; the 
pyloric appendages of Acanthocottus are proportionally much shorter and thicker, 
and variable in length. 
In Triglopsis these appendages are seven in number, six developed ones nearly 
equal in size, intermediate in length between those of Cottus and Acanthocottus, 
and a rudimentary one. The pyloric appendages present some variations which 
make scattered observations very uncertain when used in the characterization of 
the groups. 
The urinary bladder is very thin, pyriform, or elongated, situated above the 
ovaries. Cottoids have no air bladder. 
The kidneys are so close together that they seem to constitute a single organ, 
slender and elongated in shape; they extend nearly to the two-thirds of the abdo- 
minal cavity adhering to the vertebral column. 
The ovaries are pouch-like bodies, having a common duct. Sometimes after the 
spawning season, when they are reduced to their smallest size, they appear then 
under the shape of two elongated and cylindrical processes, differing only from the 
urinary bladder, by the thickness of their walls. When expanded by the develop- 
ment of the eggs, the walls become so thin and transparent that their contents 
may easily be seen: In this state these organs are elliptical. 
At the upper wall of the ovarian sac there exist membranous folds in which the 
eggs are developed; the lower wall remains free from any such folds. When the 
eggs are mature, and ready to leave the body, they separate from these folds; but 
instead of dropping into the abdominal cavity, as is the case with many fishes, they 
are kept in the ovarian pouch, which leads into the single oviduct, whose opening 
is placed behind the vent. 
The eggs themselves are very large compared to the size of the fish. 
The spermaries are very slender, much elongated, extending from the oesophagus 
