908 



SCANDINAVIAN IISIIKS. 



The clearest cxin'csisioii of the evolutional coui'sc 

 of the form-series we here find in tlie relation lietween 

 the depth of tlie snout ut the rostral protuberances 

 and the length of the maxillaries: the former increases 

 and the latter decreases, so that the averages rise with 

 great regularity from left to rigiit in tlie last line but 

 one of the table. Yet tiiese averages, as we have men- 

 tioned, must be considered with reference to the size 

 of the specimen: among small specimens both of i\"/?s- 

 soiiii and lavaretus for example the m;inocentrous show 

 a smaller average than the pycnocentrous; but the law 

 of evolution tells us, according to the preceding table, 

 that if the former had been ]>ermitted to attain a 

 sutticient size, their jiercentages for this relation would 

 undoubtedly have risen enough to fill their place in 

 the series. 



Ik'aring this residt in mind, we can easily' deter- 

 mine the systematic value of the peculiarities which 

 seem to characterize the flwyniad wliere it lives under 

 exceptional conditions. In Enare Tra-sk for example 

 (Finnish Lapland) it sometimes develops the beaked 

 form" at a length of 14 or 15 cm. and with a depth 

 of snout persistently answering to the shallow snout 

 of the typical hlasikar, though it is cjuite manoeentrous, 

 with no more gill-rakers than a. poJcnr. But to coin 

 a special name for such a form, is of ([uestionable 

 utility, for a similar prolongation of the snout, though 

 not quite so great, may be observed in young hlasikar, 

 for example from Qvickjock, where they attain matu- 

 rity at about the same size''. 



The relation between the two groups, the one*^ 

 collected round the hlasik type, the other** round the 

 fetsik type, is evidently the same as that between 

 fniffa and sular among the Salmons. Thej' come so 

 near each other that constant characters to distinguish 

 them cannot be adduced; the one is a more advanced 

 development of the other, and they intermingle in their 

 sjiawning operations'. However unlike the differentia- 

 tion of form may be in localities at a distance from 

 each other, variations as great may be observed in the 

 same water, the extremes of the form-series appearing 

 side by side. No wonder then that ichthyologists have 



failed sliar]ily to detiiie local \arieties, though a more 

 than adecjuate number of names have l)een proposed 

 to this end. 



The coloration of the (nvyniad is essentially the 

 same as that of the ^ endace, and is subject to the 

 same variations of light or dark tone. The back is of 

 a lusti-ous steel-blue, whence the name of blasik, or 

 black, in wliich case the latter colour also extends to 

 the up]jer part of the head and forward over the snout, 

 or, like the top of the liead, of a more greenish gray 

 tint and more or less transparent, the transparency being 

 most noticeable in the occiput and the snout, though 

 the tip of the latter is commonly brownish black. The 

 sides ut the body have a silvery lustre, l>ut often pass 

 into a dirty gray, which colour has given rise to the 

 name of grdsik, and is sometimes uniformly distributed 

 over the middle of the sides, but generally more pro- 

 minent at the limits between the longitudinal rows of 

 scales belo^\■ the lateral line. The ventral side is of a 

 purer white, at the middle milky white. The sides of 

 the head partake in the silvery lustre of the sides of 

 the body: but on the gill-cover this hue frecjuently 

 passes into a brassy lusti'c: and the articular process 

 of the operculum is of a brownish black colour, which 

 is continued back in a longitudinal strijie. The yel- 

 k)wish colour often extends to tlie cheeks and jaws. 

 The lower part of the head is of the same colour as 

 the Ijelly. No less variable is the coloration of the 

 fins. Sometimes all of them are entirely black; but in 

 the lighter varieties they may all be light, greenish 

 gray or transparent. As a rule, however, they are 

 light (gray or dashed with red) at the base, but the 

 outer ]Kirt of the tin-membrane is dark, grayish or 

 brownish blaik, this being due to a rarer or denser 

 agglomeration of lirownish black pigment, which is 

 sometimes merely besprinkled on the ti])S of the pec- 

 toral and ventral fins. The same pigment is frequently 

 scattered in tine dots over the skin of the whole body', 

 and usualh' collects on the middle or bottom of the 

 dorsal tin, on the upper part of the head, on the inner 

 (hind) surface of the pectoral and ventral tins, and 

 sometimes here and there on the sides of the l)ody. 



" Smitt, ). c. tafl. V, tig. 89. 



'' S.MrrT, 1. c, tab. metr. X, No. 1G9. 



" Fatio's Coregonus dispersus. 



'' Fatio's Coregonus balleus. 



' Fatio has recognised a bloiiding oi characters in liis "species coinposita", Coregowis Stiiiiteri {Fiie Vert. Siiifsse, vol. V, p. 270). 



■^ They are sometimes entirely wanting in the light varieties. 



