362 



SCANDINAVIAN FISHKS. 



Schiodtk", IJKiciiKirr''. ;ni(l A. AdAssiz' have Inid tlio 

 luiiiulafioM of niir present kii()\\iedg'e of tlie changes 

 of (levelopHient through wliich this peculinrity ciHues 



to pass. 



Diu'ing the early development of the embryo in 

 the egg and the first part of their independent existence 

 the Flatfishes are fully symnietvieal, like other verte- 

 brates, ^lost, if not all, of the Flatfishes leave their 



surface, especialh' on calm and clear da\'s. \\'ithin the 

 island-lielt of I'lohusliin Mai.m found tlu' \i>ung of tlie 

 Brill swimming in this way in shallow water, in a liay 

 off Stromstad; and inider similar <ircumstances, near 

 Kanso off Gothenburg, he found a young specimen, 12 

 mm. l(jng, of the Sole, that had already undergone a 

 great portion of its transformations. In the samjway 

 too, in the harbour of Copenhagen, Mullei; took witii 



Fig. 08. Cliiuiges of g-rowtli in the larviu of a Pleuronecteti (.iiiierk-niiiis: n, a larv.-i iilioiit 4 nun. long, a day or two after the liatcliing of 

 the egg, with fully .syiiinietrioal eyes. Peotoral fins well-developet). Larval vertical tin e.xtemling without a hreak from the occiput lound 

 the tip of the tail to the venl, the ventral part being somewhat broader than the dorsal. Ii. somewhat older and much less transparent than 

 the preceding specimen. -Vt the caudal end the notochonl has begun to be elevated (tlie beginning of the heleroi'ercal stage), and (Uie or two 

 very indistinct caudal rays have appeared in the vertical tin beneath it. c. a larva 5 mm. long, with a far greater rmmber of rays in the 

 distinctly heterocercal caudal fin, and witli the segmentation of the spinal column more distinct, d, 7 mm. long, with indications of the 

 separation of the caudal fin from both llie dorsal and the ventral vertical fins, which are both still without rudiments of true rays. f, of 

 tile 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. Ag.\ssiz. 



eggs to develop freelv floating in tlK> sea — the eggs ;i hoop-net the young specimen of the lirill whicli is 

 of the otliers lie l(;osc on the bottom or are looseh' 



iittaehed to seaweeds or otlier objects — and (hiring the 

 first days of tlieir existence the Aoung are found swim- 

 ming about, like tlie frv of other fishes, often at the 



de.scribed b\- SchiOdte; and the cireumsttinces were the 

 same when A. Agas.siz found outside the htirbour of 

 New])ort, (piite near shore, the transparent young of 

 the liothoid form which he c(jnsidered to beloniz' to the 



" Xaturh. Tidskr. Kbhvn, ser. :i, vol. V. p. -.267, tab. XI. 



'' Arch. Anat., Phys. etc., .Jahrg. 1S74. p. 100; Stzber. Ges. Naturf. Fr. Berlin, 1874, p. 85. 



' Development of tlie Flounders, Proc. .\mcr. Acad. .Vrls and. Sc, vol. XIV, 1878, plates III — X. 



