J. Johnstone 
413 
suggested above, is probably an invertebrate which is eaten both by the 
collateral hosts {Trigla, Gadus etc.) and by the final, or adult hosts 
(Skates and Rays). But the distribution of the Plerocercoid larvae in 
the collateral hosts is so much commoner than the distribution of the 
adult worm in the final hosts, that it seems very probable that the true 
larval host is an invertebrate, regularly eaten by Teleosts belonging to 
the genera mentioned, but only exceptionally eaten by Skates and Rays. 
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