362 
SCANDINAVIAN FISHES. 
Schiodte", Reichert*, and A. Agassiz" have laid the 
foundation of our present knowledge of the changes 
of development through which this peculiarity conies 
to pass. 
During the early development, of the embryo in 
the egg and the first part of their independent existence 
the Flatfishes are fully symmetrical, like other verte- 
brates. Most, if not all, of the Flatfishes leave their 
surface, especially on calm and clear days. Within the 
island-belt of Bohuslan Malm found the young of the 
Brill swimming in this way in shallow water, in a bay 
off Stromstad; and under similar circumstances, near 
KansO off Gothenburg, he found a young specimen, 12 
mm. long, of the Sole, that had already undergone a. 
great portion of its transformations. In the same way 
too, in the harbour of Copenhagen, Muller took with 
Fig. 98. Changes of growth in the larval of a Pleuronectes americanus: a , a larva about 4 mm. long, a day or two after the hatching of 
the egg, with fully symmetrical eyes. Pectoral fins well-developed. Larval vertical fin extending without a break from the occiput round 
the tip of the tail to the vent, the ventral part being somewhat broader than the dorsal, b, somewhat older and much less transparent than 
the preceding specimen. At the caudal end the notochord has begun to be elevated (the beginning of the heterocercal stage), and one or two 
very indistinct caudal rays have appeared in the vertical fin beneath it. c, a larva 5 mm. long, with a far greater number of rays in the 
distinctly heterocercal caudal fin, and with the segmentation of the spinal column more distinct, d , 7 mm. long, with indications of the 
separation of the caudal fin from both the dorsal and the ventral vertical fins, which are both still without rudiments of true rays, e, of 
the same length as the preceding specimen, with the primary tip of the tail forming a distinct lobe above the rudimentary caudal fin, and 
with rudiments of true rays in the future dorsal and anal fins. Larva still perfectly symmetrical. After A. Agassiz. 
eggs to 'develop freely floating in the sea — the eggs 
of the others lie loose on the bottom or are loosely 
attached to seaweeds or other objects — and during the 
first days of their existence the young are found swim- 
ming about, like the fry of other fishes, often at the 
“ Naturh. Tidskr. Kbhvu, ser. 3, vol. V, p. 267, tab. XI. 
6 Arch. Anat., Phys. etc., Jahrg. 1874, p. 196; Stzber. Ges. 
c Development of the Flounders , Proc. Amer. Acad. Arts and. 
a hoop-net the young specimen of the Brill which is 
described by Schiodte; and the circumstances were the 
same when A. Agassiz found outside the harbour of 
Newport, quite near shore, the transparent young of 
the Bothoid form which he considered to belong to the 
iturf. Fr. Berlin, 1874, p. 85. 
c., vol. XIV, 1878, plates III — X. 
