892 PROFESSOR W. C. M'INTOSH AND MR E. E. PRINCE ON 



and a similar prominence (pre-anal) corresponding to no structure in the adult fish, and 

 not comparable to the first anal of the Gadidse, occurs between the ventral and the anus.* 

 When a week old, these portions, which correspond to the regions of the permanent fins, 

 are denser, the other parts being very thin, and apparently undergoing absorption. 

 The embryonic rays are now distinct. Meanwhile the blood-vessels begin to ramify- 

 in the " fatty " fin (PL XXVIII. fig. 3), and the capillaries in front and behind the 

 primary series are on the ninth day increased; they soon, indeed, extend throughout the 

 entire length of the fin. Several indications of true fin-rays occur in the first dorsal, and 

 at the end of a fortnight the embryonic marginal fin has, to the naked eye, nearly 

 disappeared, so that the permanent fins are more boldly marked. Pigment appears in 

 both dorsal fins at the same period ; while pale capillaries ramify in the anal fin, and 

 stretch nearly to the tip. They probably also develop in the dorsal and ventral ; but 

 they were not seen. The marginal (embryonic) fin is now almost absorbed, except in 

 the interval between the ventral fin and the anus. 



Between the fourth and fifth weeks, the dorsal and anal fins show the cartilaginous 

 rays, while the membranous parts between them are widened and coloured by numerous 

 yellow and brownish pigment-corpuscles. Thirteen rays occur in the dorsal, and the 

 same number in the anal fin, and the interspinous elements produce wavy marks beyond 

 the muscle-plates. Both fins have crenate borders, as in the tail at this period ; while 

 the adipose fin presents a fibrillated aspect, and has a network of fine blood-vessels. All 

 the fins are proportionally larger than in the adult, as observed in the outline of an 

 average specimen (PI. XXII. figs. 10 and 11). In minute structure the dorsal and other 

 fins already present most of the characters of the adult. Thus, at the anterior part of 

 the dorsal, are two narrower and shorter rays, the first a simple spike, the second con- 

 sisting of two which form a loop. At the base of the larger rays is a projecting median 

 point, and the terminal process is long, and almost unciform. The pigment is chiefly 

 placed on the cartilaginous rays. 



In considering the condition of the median fin-rays of these young fishes, it will be 

 observed that on the thirteenth or fourteenth day the dorsal of the soft-rayed salmon 

 corresponds nearly with the condition in the adult, but in the anal fin the number of rays on 

 the tenth or the twelfth day, viz., thirteen, is in excess of the number in the adult. In this 

 respect, however, it is doubtful how far authors in numbering the rays have anatomically 

 examined the parts, or how much they have depended on external appearances. On the 

 other hand, the osseous rays in the dorsal of the young wolf-fish seem, if Day be right, 

 to be fewer than in the adult, viz., 71 as compared with 72 or 74 (Day), while the rays 

 in the anal present a similar condition, viz., 44 in the young as against 45 to 46 in the 

 adult. An examination, however, of the skeleton of a fine adult in the University 

 Museum here shows that the number of the dorsal fin-rays exactly corresponds with that 

 of the young forms just mentioned, and so with the ventral. There may be variation ; 



* The outlines of the fins of the young salmon seem to differ considerably from those of the larval Lochleven 

 trout, as shown by Mr J. T. Cunningham, Trans. Boy. Soc. Edin., vol. xxxiii. pi. i. fig. 4. 



