of the Fishery Board for Scotland. 



61 



was a ripe male. The fish were in sufficiently good condition. One cyst 

 taken from a nerve had an embryo that appeared a little further advanced 

 than those previously examined. 



Parasites similar to the above were found in the skin of a small cod 

 which had no tail. (Vide p. 57.) The fish in its mutilated condition 

 measured 10§ inches (27'5 cm.) in length. The cysts were of approximately 

 similar size to those of the whiting, and had black pigment surrounding 

 them. One cyst measured '35 x '27 mm.; it had a thick rind. 



Two small cod and two little lythe were'infected with the same Trematode, 

 The cod measured 7 '5 and 8 cm. in length, while the lythe were 10 and 

 10*5 cm. long. One of the lythe was examined. The spots resembled 

 exactly those on the whiting. They were scattered over the sides, fins, and 

 eyeball. None was made out in the spinal nerves. One cyst measured 

 •35 X *25 mm. 



The parasite is evidently Gasterostomum gracilescens. 



Johnstone observed this species in the brain of Gadus ceglefinus and 

 Phycis blennoides. He also found a Gasterostomum (sp.) encysted in the 

 muscles of Pleuronectes platessa. The cysts were, in the case of the larger, 

 faintly brown, or dull-red in colour. Lebour found the former species common 

 in the nerves of the Gadus ceglefinus, Gadus callarias, Gadus merlangus, on 

 the Northumberland coast. She does not mention its occurrence in the 

 skin. 



Nicoll* observed a very similar parasite (Distomum, sp.) in Cottus bubalis. 

 He found the muscles, skin, bones, and layers of the eye impregnated with 

 small masses of black pigment, accompanied by cysts containing Trematode 

 cercarise. The only parts of the fish not affected were the brain and ab- 

 dominal organs. The pigment-spots appeared to follow the course of the 

 blood-vessels, and they are probably spread throughout the body by means 

 of the blood. 



Nematodes in the Muscle of the Cod ( Gadus callarias ). 



A codling was observed to have a large number of nematodes scattered 

 through the muscles. The worm lay coiled up in a cavity which it has 

 formed by pressing apart the muscles (fig. 26). The muscles do not appear 

 to be injured at the part. The nematode is reddish- coloured at either 

 extremity. It is enclosed in a light skin of connective tissue, and the cyst 

 itself is lined with fascia which is bound to the muscles. The worm has 

 thus two investments. The cyst is sometimes red-coloured owing to its 

 being well supplied with blood vessels. The coils of the nematode pass 

 through the fascia which often shows well developed blood plexuses, (bpx., 

 bpx.', fig. 20). In one case a pillar of tissue joined the floor of the cyst to 

 the roof (fig. 31). The nematode was coiled round the pillar which was red 

 with blood vessels. 



A cod fillet containing similar worms had been prepared in the usual 

 method. It had been in pickle for half-an-hour, and then had been in the 

 smoke-kiln for the customary period, viz , from three-quarters of an hour to 

 two hours. It was received on 17th December, and was kept until the 30th 

 of the same month, by which time it was smelling offensively. Live worms 

 were dissected out at intervals from the 17th to the 30th. The fish was, so 

 far as it could be judged by smell, good on the 25th. 



A piece of cod infected with these parasites was dried in the open air with- 

 out any preservative. Three months later the fish was examined. It was 

 quite hard. The worms when removed from the muscle were translucent, 

 amber in colour. They were dry, flattened, and tough. When one was put 



* Nicoll : "A Contribution towards a Knowledge of the Entozoa of British Marine 

 Fishes." Ann. and Mag. Nat. Hist., xix. (7), 1907, p. 66. See also ib. xvii. (7), 

 1906, p. 148; xx. (7), 1907, p. 244: iii. (8), p. 237: iv. (8), p. 1. 



