648 



SCAN'DIXAVIAN FISIIKS. 



Storm, N. Vid. Selsk. Skr., Trondhj. 1883, p. 15; Mun., 

 HcKE, Fiscli. Osts., p. 66; LiLU., <S'u., JVorg. Fisk., vul. I, 

 p. 343; M6b., Nature, vol. XXXIX, No. 9ii8 (Dec. 13, 1888) 

 HcKE, Ofvcrs. Vet.-Akad. Forh. 1889, p. 395. 



ddHerosteus biaculeatus, Shaw fex. Pen.n.) Gen. Xool., vol. 

 IV, p. 608. 



Gnxturosteus tracliurus + (! . gyiiinuni/i (leiiinis) + 0. ariji/ropo- 

 mus+G brachycentrus + G. tetracunthus + G. noveboracensis 

 + G. niger, Cuv., Megn. Anim., ed. 2, torn. II, p. 170; + G. 

 semiarmatus+ G. semiloricahis, Cuv., Val., Hist. Nat. Poiss., 

 vol. IV, pp. 493 ct 494; G. loricatus+ G. dimidiatus, Reinh., 

 D. Vid. Selsk. Math. Naturv. Afh., VII (1838), pp. 114 et 

 119; G. aculeatus + neustrianus + semiloricatus + semiarmatus 

 + leinrus + Bailloni + argentatissimus + elegans, Blanch., Pom. 

 fi. eaux douces Fr., pp. 213 — 236; G. aculeatus + ponticus 

 + noveboracensis + .tuppositus + obolarius (:^) + loricatiis + niger 

 + serratus + neustrianus + semiarmatus + semiloricatus -^texa- 

 iius + leiurus + Bailloni + algeriensis + plebeivs + inopinatus + 

 argeyitatis.mnus + elegans + i.^landicus + biaculeatus + microce- 

 phalus + argyropomus + brachycentrus + tetracanthus + spinu- 

 losvs, Sauv., Nouv. Arch, ^fu.^i., torn. X, pp. 9 — 25; (r. 

 microcephalus + biaculeatus + atkinsii (ex ViEkv') + acideatns, 

 JoBD., GiLB., Bull. U. S. Nat. Mus., No. 10, p. 395. 



Ofc. Tlio great miinber of noiuinal species tliat liave been estab- 

 lished, according to the above list of synonyms, in the endeavour 

 to elucidate the inconstancy of form among Three-spined Stickle- 

 backs, is merely a significant token of the lengths to which this in- 

 constanc}' may run in a species that sometimes occurs in enormous mul- 

 titudes, is found in far distant localities both in salt water and in fresh, 

 and botli in form and colour shows marked sexual distinctions. 



The Thi-ee-spiiied Sticklel)ack attains a length of 

 at least aljout 9 cm. Our largest specimen is a female 

 from Greenland which measures rather more than 91 

 mm. from the tip of the snout to tlie end of the middle 

 I'avs of tlie caudal tin, or 93 mm. from the tip of the 

 lower jaw to the end of the outer caudal rays". The 

 form of the bod}' reminds us strongly of the Horse- 

 Mackerel, being fusiform Avith strong lateral compression. 

 The body is deepest across the pelvis at the articulation 

 of the ventral spines, ^\•here the depth is aljout ' 5 of 

 the length of the body, varying individually between 

 IX'/a fiid 2272 % thereof. Tlie thickness at the same 

 spot is about half the dcptli, varying individually be- 

 tween 44 and 57 % thereof. Except during the spawn- 

 ing-season, when the organs of genei'ation become tumid 

 and render the bod}' more terete, the thickness is almost 

 uniform from tlie eyes back to tlie strongly compressed 

 base of the caudal tin, the sides being flat throughout 

 the forepart of the bod\', t)ut witii sharji c;iriiuT on 



their posterior pai'ts, exce])t in the variety (/i/ini/ttn(s, 

 \\hicli is without caudal plates, and in which the sides 

 of the tail are also Hat. The doi'sal profile between the 

 h(^ad and the soft-rayed dorsal tin and the ventral pro- 

 tile between the head and the anal tin are usually com- 

 paratively straight or only slightly convex, M'hile the 

 upper and lower contours of the head in front and of 

 the tail behind are more sharply convergent. Some- 

 times, however, especially in the females, which gene- 

 rally show a deeper form of body, the entire upper and 

 lower profiles of the body run in unbroken curves. The 

 external form is also affected to a, considerable extent 

 by the more or less advanced development of the co- 

 vering of plates, this being the origin of most of the 

 nuinerous different names by which the species has 

 been known. 



Tlie whole covering of plate-armour shows fairly 

 great individual variations both in extent and in strength. 

 In its strongest form it consists of comparativeh' thick 

 osseous growths in the skin, externally resembling Ga- 

 noid scales, granulated and striated by grooves and 

 ridges, the latter rough with small granules. But, as 

 Heincke has remarked, both the thickness and the rough- 

 ness may be reduced, to the greatest extent, as a rule, 

 in the Three-spined Sticklebacks that inhabit brackish 

 or fresh' water, or belong to more southern regions. 

 Still forms with extremely reduced plate-armour also 

 occur in the Arctic regions, as for instance in (treen- 

 Land, whei'c the Sofa Expedition of 1883 took a number 

 of small specimens of the gi/miiun(^i'orm in a lake near 

 Ritenbenk (North Greenland). These specimens, like the 

 Italian arc/i/roponms, have only thrtse jjlates on each side 

 of the body, namely the three that adjoin the ascending 

 lateral disk of the j)elvic bones. 



The plate-armour of the back \\'e liave already exa- 

 mined for the most part, and we need only add that 

 here, as in the Fifteen-spined Stickleback, the soft-rayed 

 dorsal fin rests on a row of interneural plates (here 

 about 13, i. e. ■ — excluding the plate of the last spinous 

 ray — one for each raj' and one more behind the fin). 

 This statement also applies to the anal fin, which gene- 

 rally has 11 interhtemal plates at the liase, the first 

 su])porting the si>inous ray and the last two usually 



" Thus almost exactly equal to tlie largest specimen in Copenhagen Museum, according lo Hansen (Zool. Dan., 1. c.). .\ccording to 

 Pai.las it attains a greater size. His Gasteracanthus cataphractus from Kamchatka seems to be simply tlie typical Three-spined Stickleback, 

 lint is slated to attain a length of 122 mm. (lougitudine pollicum sesqniquinque). Cf. also Tii.ESius, Mem. Acad. Petersb., torn. Ill (1809 

 — 10), p. 220. 



*■ Already remarked by KitoYEH (1. c, p. 180). 



