III. COTTOIDS OP NOKTH AMERICA. 31 



10. THE ALIMENTARY CANAL, URINARY BLADDER, AND OVARIES, IN COTTOIDS. 



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 Coitus 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 



