112 TRAXSACTIOXS LIVEEPOOL BIOLOGICAL SOCIETY. 



Fixation plays strange tricks with the appearance of these 

 organs, and sometimes they are widely expanded, with 

 almost invisible walls, while at other times their Inmina 

 are reduced to the merest chinks, and the walls may be 

 quite thick. 



The situation of the worm is also unusual. As a 

 rule a Tetrarhynchid larva inliabits the body cavity, but 

 it is enclosed in a cyst, derived partly from the larval, 

 partly from the host's tissues. Coenomorphus, however, 

 lives freely in the peritoneal cavity attached by means of 

 its suckers and hooks in the manner of an ordinary 

 Cestode. 



What we doubtless have here is a " permanent " 

 larval stage. Gadus vireiis is, for Coenotnorphus, a 

 collateral liost, not a true intermediate host. I have argued 

 elsewhere* that this is the nature of the Teleostean 

 hosts of Tetrorli i/iirhus erinaceus, which Cestode inhabits 

 only the Rays in its adult condition, but a number of 

 Teleosts in the plerocercoid stage. It is difhcult to 

 believe that the Ray is infected by eating such fishes as 

 Gurnards and Whiting, in which fishes plerocercoid 

 larvae of T. eviiKweus are, in my ex})erience. ahrays 

 found. The true hirval host is no doubt some small 

 invertebrate, a mollusc or crustacean, and both the 

 Teleosts and Elasmobranchs are infected by eating these 

 creatures. The plerocercoid and iuhilt stages are, on this 

 view, collateral ones, as are the hosts. The same view is 

 also taken by Southwell with regard to tlie life history 

 of Tetrtir/i i/)ii-/i i/s iinmvi factor , wliicli inhabits both 

 Teleo.sts and Ehismobi'aiicJis in Ceyh)n waters. l)ut the 

 Teleost in this case is, according to Southwell, a cuJ-dc- 

 sac in the life-history. 



Coenomorphus is therefore probably a Tetrarhynchid 

 * Parasitology, Vol, IV, No. 4, January, 1912, p. 368. 



