29 



liy the developinent ot' the Hsli, esjieciuUy tlie loss of tlic spine.s on tlie 

 lieud. From stages like fig. 4 we come easily to the younger spiny ones, 

 fig. 1 — 2. The great Duinber of fin rays which we find in the here raeutioned 

 specimens, removes tlieni, moreover, so decidedly from Z. norvegiciis that 

 there can be no dcubt now that the series on table I, fig. 1, 2, 3, 4, 5, 

 belongs to Z. punctaius, to whicli the spinj' larvæ must consequently be 

 referred. But I must coufess that it is only after I have become acquaiuted 

 witli these above mentioned cogent reasous, that I refer the spiny larvæ to 

 this species; originally I thought that they belonged to Z. norvegicnsJ) 



From the above it follows that the smootli young fish must belong to 

 Z. norvegicus. The rather high form of tlie body (cmp. my table I, fig. 

 <6 — 7), certainly does not remind you much of the grownup Z. norvegicus, 

 whieii is rather slender; but the decidedly low number of rays does, and so 

 does the form of the lower jaw. The number of rays in the dorsal, in the 

 specimens I know (c. 7), is but little in excess of 80, though 82 and 85 

 are known. I am greatly astonished that M'Intosh has seen a smooth 

 young one with c. 90 rays in the dorsal, but it is possible, of course, that 

 he is right. Both Holt and U. CoUett have sent me several young ones of 

 the smooth type, by which I have been enabled to see that the trans- 

 formation from pelagic young fish to the bottom stage takes place when the 

 fish is about 10 mm in leugth, as in Z. pundatns. That I have nou-trans- 

 formed specimens of Z. norvegicus from the Shetland Islands, still pelagic, 

 c. 11 mm long, cannot cause any astouishment, when we know the variations 

 the development of flatfislies is generally subject to under unetjual conditions, 

 and that the transformation may be accompanied by a shorteniug of the 

 length of the fish. In fig. 8 I give a picture of a 13 mm long Z. norvegicus 

 from Norway [CoUeK), because it is pretty well preserved, and shows accord- 

 ance with the grownup fish in the number of fin rays, as well as in the 

 form of the body, tiie way in which the eyes are placed, the form of the 

 mouth, the pigmeutation and the size of the caudal fin. Collett has also 

 immediately seen to which species it belongs. I believe that the two series 

 of figures on table I, 1 —5 & 6 — 8, will make it impossible in future to doubt 

 that Z. ]nmch(tus has spiny larvæ with striped pigmeutation, and that Z. 

 norvegicus has smooth ones. 



Besides the young ones belonging to the two said series, there are, in 

 the collections gathered by the Tlior, two which perhaps have been taken 

 near the bottom, but whicii, to judge by their glassy appearauce, are pelagic 

 young fish with "otocystic" spines and evidently belong to quite another 



') The 10 mm lonu; Z. nor rer/ i c ns wliioh I mentioned in "De danske Farvandes Plank- 

 ton, I", must therel'ore be referred to Z. jnmctatus (Kijl. danske Vulensk. Selskabs Skrifter, 

 (i. R, natitrr. og math. Afdelini/, XII, 3, 1903, p. 260 & 250). — When tlie liiology ot 

 these flshe.s has become further elucidated on the basis of the new iiarticulars, information 

 of the results will be given in the foUowing pajiere. 



