DEVELOPMENT AND LIFE-HISTOKLES OF TELEOSTEAN FISHES. 843 



the tip of the tail. The pigment is also scattered along the sides of the head somewhat 

 symmetrically, and produces a characteristic appearance. 



The mandible, about the eleventh day, has the form of a remarkable process in front. 

 The larva differs from Agassiz's figure of Pleuronectes americanus, and shows much more 

 pigment. The anus is open or nearly so. Instead of the hollow urinary vesicle behind 

 the rectum a merely granular band passes downward parallel to the anal tract. 



After the yolk has been absorbed, the little flounder presents a somewhat deeper 

 aspect from increase of the marginal fin, as well as the more prominent pigment on it. 

 Eight touches of black pigment occur at the margin of the dorsal fin and four behind 

 the vent inferiorly. The large yellowish pigment-corpuscles (about eight in number) are 

 confined to the body, only a series of minute ones being distributed on the marginal fin, a 

 single speck generally existing in the centre of each blackish area. The latter are larger 

 ventrally than dorsally. The trunk and intestine are minutely flecked with black points. 

 The anterior region of the abdomen has a few yellowish specks. Ventrally about three 

 yellowish touches occur along the edge of the muscle-plates. The eyes are bluish silvery. 

 A dark mass of pigment lies internally at the pectorals, probably in connection with 

 the segmental ducts. The anus is at the margin of the fin. Corpuscles occur in the 

 heart. The mouth is widely open, and slight movements of the mandible take place. 



As already mentioned, the ova of this species are very hardy, and the larvae 

 after emergence will live for some days in a very small quantity of water, even if 

 unchanged.* 



After the foregoing stages are passed, the little flounders are still pelagic, swimming 

 about with eyes on both sides of the head. Like other flat fishes, however, as they get 

 older they seek the lower parts of the water, though the eyes are still lateral and 

 symmetrical. They are obtained by aid of the mid-water net at various stages in April, 

 viz., some with the left eye still on its own side, though advanced a little and more 

 prominent ; others show the eye on the edge in front of the dorsal ; while in a third 

 series the left eye has gained the right side. 



In April very transparent flounders, about 12 to 14 mm. in length, occur freely 

 in St Andrews Bay, and also in the sandy pools amongst the rocks. A few weeks 

 later (May 24) many occur at the mouth of the lade, which pours a fresh-water stream 

 into the harbour, and are caught while swimming at the surface in company with Mysis 

 vulgaris, young eels, and sticklebacks. These specimens had the eye at the edge, just 

 as in the case of many caught in the sandy rock-pools. Moreover, each of the examples 

 referred to had a parasitic Anceus Edwardi attached externally, generally near the 

 margin of the muscle-plates at the base of the dorsal fin. When the crustacean was 

 removed a deep pit in the tissues of the flounder showed the point of attachment. 

 Further the Anceus immediately sought a new place, and began to pierce a fresh portion 

 of the skin with its sharp spine-like gnathites, and tenaciously held to the fish. After 

 boring a little, a tongue-like process was thrust out, apparently for suction. The irrita- 



* Vide remarks in Report of Roy. Commiss. on Trawling, 1885, p. 363. 



