92 



MARINE AND FISHERIES 



6-7 EDWARD VII., A. 1907 



acidia). During this time they must find suitable hosts (snails, annelids, crabs, &c.), 

 into the soft parts of which they penetrate. Here they remain immature, but their 

 locomotory and sense organs degenerate, and they become so far transformed and so 

 entirely different from either the free-living miracidium or the mature adult 

 as to be completely unrecognizable, in which case the specific identity can only be 

 made out by finding intermediate stages. It may also happen that the larva in the 

 snail (called a sporocyst) does not transform directly or slowly into the adult form, 

 but by a kind of internal budding produces clusters of cells that develop into new in- 

 dividuals, the old individuals becoming disintegrated and destroyed. The primary 

 intermediate host may, in some cases, serve as food to a secondary intermediate host, 

 which in its turn falls prey to the final host, in each case the parasite suffering a 

 change of environment. Sooner or later — ^but always in the definitive host (a fish) — 

 the parasite reaches its final development, becoming sexually mature and producing 

 eggs. 



The list of species studied at the Marine Biological Station in the course of my in- 

 vestigations is as follows — 



I. TURBELLARIA. 



1. Micropharynx parasitica Jagerskiold. 



(=Pseudocotyle fragile Olsson). On the skin of the barn-door skate, i^aja 

 Icevis Mit. 



II. EOTOPARASITIC TrEMATODES. 



1. Tristomum molae, Blanchard. On the skin of the sun-fish (Mola mola L.). 



2. Tristomum coccineum, Cuvier. On the gills of the sword-fish (Xiphias 

 gladius L.). 



3. Epihdella hippoglossi, 0. F. Miiller. Skin of halibut (Hippoglossus hippo- 

 glossus L.). 



4. Acanthocotyle verrilli. Goto. Skin of starry-ray (Raja radiata Don.). 



5. Pseudocoiyle apiculatum, Olsson. Skin of dog-fish (Squalus acanthias, L.). 



6. Udonella caligorum, Johnston. Attached to tails of specimens of Caligus 

 which are themselves parasitic Crustacea on the skin of the cod-fish (Gadus callarias L.'). 



7. Octocotyle scomhri, Kuhn. Gills of mackerel (Scomber scombrus' L.). 



8. Dactylocotyle denticulatum, Olsson. Gills of pollack (Pollachus virens, L.). 



9. Dactylocotyle phycidisi, Parona et Perugia. Gills of hake (Phycis chust 

 Walb.). * 



10. Anthocotyle merlucii, van Beneden et Hesse. Gills of silver hake (Merluccius 

 bilinearis Mit.). 



11. Onchocotyle ahhreviata, Olsson. Gills of dog-fish (Squalus acanthias, L.). 



III. Endoparasitio Trematodes. 



1. Distomum veliporum, Creplin. In the oesophagus, stomach, and intestine of 

 the barn-door skate (Raja laevis Mit.). 



2. Derogenes varicus, O. F. Miiller. Mouth, oesophagus, stomach of — 



Salmon (Salmo salar L.). 



Cod (Gadus callarias L.). 



Haddock (Melanogrammus aeglefinus L.'). 



Pollack (Pollachius virens L.). 



Herring (Clupea harengus L.). 



Smelt (Osmerus mordax, Mit.). 



Rose-fish (Sebastes marinus L.). 



