SEA SCOKIMON. 



183 



Willi ,il;(' cuiiic (listiiict cliaiiges in I lit' length of but t'roiii a systematic point of view this "degeiieracj'" 

 the liead and ol tlu' jaws, which become lai'ger, even | indicates a transition to tiie hnhalis group. In tlie 



in relative size; in tlu; distance between tlie Ix'ginning 

 of tile lirst dorsal fin and that of the second, and in 

 the distance between the foniier ;ind the tip of the 

 snout, both of which nieasurenients also increase; in 

 the distance between tlie ventral fins and the be- 

 ginning of the anal hn and in that between the latter 

 and the ti]) of the snout, wliicli also increase; and 

 lastly in the longitudinal diameter of the eye, which, 

 on the other hand, diminishes with aire accordiu"' to 

 the rule. In the length of the head scarcely any sexual 

 difference can be detected; but in all the rest of these 

 changes of growth the females take the higher place in 

 the scale of development. The most constant external 

 difference between the sexes, the length of the ventral 

 tins, naturally becomes more marked with age. It may 

 be expressed, at least in specimens 150 mm. or more 

 in length, as follows: in the males it is more, in the 

 females less, than 18 ?» of the length of the body, or 



number of the vertebra; (Jotfiis scorplus occupies an 

 intermediate position between Cotfus quudricorms, Avhich 

 has 40, and Colhis IjiiIkiI/s. which has only 29 or ?>0. 

 The \ariabilit\- of the Sea Scorpion thus suggests with- 

 out and)iguity an explanation of the origin of its kind- 

 red species. The course of development stops at dif- 

 ferent stages, has its direction fixed by a sexual cha- 

 racter, or bears the stamp of different external influ- 

 ences due to different local circumstances. 



The usual size of the Sea Scorpion in Scandinavian 

 waters is between 200 and 250 mm. In the Baltic and 

 the Cattegat it seldom exceeds the latter measurement; 

 but on the coast of Norway it grows somewhat larger, 

 and in the Arctic regions it is said to attain a length 

 of about GOO mm". The length of the head (cf. the 

 al)ove table) is about ^/.., its depth about ^5, of the 

 length of the body. The breadth of the head varies 

 considerably, and depends on the greater or less ex- 



85 % of the distance between the beginning of the first J pansion of the gill-cover, which causes a great altera- 



dorsal fin and that of the second, or 33 % of the di- 1 tion in the appearance of the head. The gape is large, 



stance between the anal hn and the tip of the snout, i and the upper jaw soraeAvhat projecting; it is moved 



Geographical separation, according to the above table, chiefly by the help of the intermaxillary bones, which 



seems to be accompanied also by an increase in the , are rendered capable of some protrusion liy their nasal 



length of the head in the specimens from Bohuslan and process. They are covered by the labial skin, which 



the Baltic, but shows its influence most clearly in the i is, as it were, rolled over them. Fine, cardiform teeth 



size of the eyes, the longitudinal diameter of which, in j are closely set in the lower jaw, on the intermaxillary 



spite of the great changes due to age, is distinctly bones and on the head of the vomer, where they are 



larger in specimens from more southern latitudes than j ai-ranged in a right angle pointing for^vards. There 



in those from the Arctic regions. We must here add are no teeth on the palatine bones or the tongue; but 



an oliservation made liv Mai.mghen, given also by Day", in the pharynx, above and below, we find two round 



that the Scandinavian specimens generally have a larger j patches, close to each other and covered with similar 



number of rays (usually 2 more) in the first dorsal fin 

 than those which live further south. It has also been 

 ascertained, says LuTiucx'', that the Arctic Sea Scorpion, 

 as a rule, has 39 (in exceptional cases 36) vertebra', 

 while the European variety has only 34" or 36''. In 



teeth. The ujiper pair of patches are larger, more jier- 

 fectlv round and set almost in the same plane; the 

 lower are smaller, flatter and set in different planes, 

 together forming a right angle in an upward direction. 

 Of the four branchial ;irches on each side the first three 



other fidies, of less variable form, these differences ( are completely free, the fourth generally united through- 



would certainly have lieen considered great enough to 

 constitute specific charactei's — here we see them de- 

 pendent on differences of age, sex or locality. Ac- 

 cording to D.VY the species has "an evident tendency 

 to degenerate the further it is from the .\rctic region". 



out its length to the liack wall of the branchial cavity 

 by a membrane behind it, which sometimes, however, 

 leaves an opening free. The gill-rakers appear in the 

 form of verrucose, spinous, bony protuberances; the 

 branchial lamella' are thin and low. The branchiostegal 



<■ Fiithes of Great Britain ami Ireland, vol. I, p. 50. 



'' Vid. Medilel. Natnrli. for., Kbhvn 187G, p. i'lTi. 



' MOREAU. Poiss. Fr.. Tome 2, p. 299. 



'' Malm. Gl^gs, Boh. F,i., p. 389. 



« Pallas, 1. c. MObius and Heincke state tlint it attains as great a length as 1 metre. 



