322 Norway. 



the embryonic lobe has advanced beyond the lower pole, showing more distinctly the brain of 

 the embryo with the ocular processes. Fig. 29. The blastoderm has advanced considerably 

 beyond the spgratorial zone of the egg, and the embryonal lobe is much narrowed and pro- 

 longed, showing an additional part of the spinal marrow. Fig. 30. The blastoderm occupies 

 almost the whole interior sphere (yolk) of the egg, only leaving a small circular space at the 

 upper pole bounded by the thickened rim. The embryo shows the first appearance of the 

 pectoral lins as a pair of small lobes at some distance back from the brain. The notochord 

 also is in this stage faintly perceived beneath the spinal marrow. Fig. 31. The blastoderm is 

 fully developed, enclosing as a complete capsule the whole interior yolk-mass of the egg. The 

 embryo is still more completely differentiated, showing the notochord, the formation of the 

 primary muscle-plates on each side of the same, and the first trace of the eye-lens and of the 

 ear-vesicles between them and the pectoral fins. At the point where the blastoderm has closed 

 over the yolk a little vesicle is seen protruding from the caudal end of the embryo. Fig. 32. 

 The embryo is still more developed, occupying considerably more than the half circumference 

 of the egg. The tail is formed as a slight projection turned on one side. The first trace of 

 the heart is seen in this stage as a small round vesicle beneath the head, without, however, yi-t 

 making any pulsations. The muscle-plates are distinctly seen on both sides of the notochord. 

 Fig. 33. The tail of the embryo is rather prolonged, advancing over the yolk, and shows the 

 clear natatory fold. The eyes are slightly pigmented, and show their lenses more distinctly. 

 The heart has assumed a fusiform shape and a somewhat obliquely transverse direction, show- 

 ing slow pulsations. Beneath the pectoral fins a small swelling is seen representing the liver, 

 and behind it the alimentary canal is about to be formed. Faint ramifications of pigment 

 have appeared en the back of the body. Fig. 34. The embryo is rather more developed, 

 encircling now the whole circumference of the yolk, the tail being considerably prolonged, so 

 as to meet or go beyond the snout : on the last the nasal pits are distinctly seen. The embryo 

 escape not rarely from the egg in this stage. (See Plate III., Fig. 37.) Fig. 35. Egg in the last 

 stage of development, eighteenth day after impregnation. The embryo now move rather 

 energetically in the interior of the egg, assuming different positions, as shown in the two 

 figures. The eyes are fully pigmentated, and the pigmentary ramifications of the body are 

 accumulated in several limited parts, forming two dark transverse bands over the tail and 

 another along the upper side of the alimentary canal. Fig. 36. Young at the moment of 

 hatching. PLATE III. (4) Development of the young after hatching, 1865-1866. Fig. 37. 

 Young recently hatched, answering the stage as shown in Plate II., Fig. 34. The yolk-sac is 

 very large and globular, and the fore-part of the body still somewhat defiexed. The notochord 

 is distinctly seen occupying the axis of the very narrow body. Fig. 37a. The same seen from 

 beneath. Fig. 38. Young a litte more developed, answering the stage Plate II., Figs. 35 and 

 36. The yolk-sac has somewhat diminished, but the mouth is still closed. The pigment of 

 the eyes and body is more pronounced. Fig. 39. Young eighth day after hatching. The 

 yolk-sac is almost entirely absorbed and the mouth is formed. The alimentary canal is dilated 

 but still simple, not convoluted. The choroidal fissure of the eyes distinct in the two pre- 

 ceding stages has disappeared, and the pigmentary bands of the body are coarser. Fig. 39a. 

 The same seen from above, showing the hoodlike expansion of the natatory fold over the fore- 

 part of the body. Fig. 40. Young on the fourteenth day after hatching. The yolk-sac is 

 completely absorbed, and the alimentary canal is about to make its first winding. The lower 

 jaw is considerably advanced beyond the upper, giving the young a rather strange 

 physiognomy. At the end of the tail a few radiating stripes are seen as the first sign of the 

 formation of the caudal fin. Fig. 41. Young of 11 mm. length, caught at the surface 

 of the sea in the latter part of May. The pigmentary stellated spots are now more evenly 

 distributed over the body, the two caudal bands being indistinct. The alimentary canal has 

 made a complete turn in the hinder part and is filled with orange-coloured contenta. Above 

 the visceral cavity is seen the air-bladder shining through the pellucid body, and at the base 

 of the pectoral fins the coraco-scapular rods are formed. The caudal fin has further developed, 

 numerous radii passing both from the upper and lower sides, the end of the notochord still 

 protruding in the middle. Two very slight folds on the upper and lower sides of the caudal 

 portion of the body are the first appearance of the two hinder dorsal and the two anal fins. 

 The ear-vesicles are considerably increased and of a somewhat triangular form. The blood has 

 assumed a red colour. Fig. 42. Young of 16 mm. length, caught at the surface of the sea in the 

 first days of June. The radii of the two hinder dorsal fins and the anal fins are distinctly seen, 



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