DEVELOPMENT AND LIFE-HISTORIES OF TELEOSTEAN FISHES. 893 



but it is remarkable that so little exists. Mr Day * had, therefore, certain grounds for 

 stating that fin-rays do not materially increase with age. 



The condition of the growing rays and of the interspinous elements in certain other 

 post-larval Teleosteans is interesting. Thus, in a section of the caudal trunk of a 

 gurnard, T 5 2 inch long, four series of interspinous cartilages are developed in the 

 connective-tissue strand which extends upwards from the neural arch. The neural spine 

 is the proximal element, and has the form of a rounded nodule clothed on each side by a 

 plate of hard hyaline tissue. The third nodule in the series is large and irregular, and 

 like the second presents a cartilaginous structure only ; but the highest nodule, lying at 

 the base of the 2nd dorsal fin, exhibits on each side a horizontal hyaline plate passing 

 outwards parallel to the plane of the flattened dorsum. The fin-rays are paired rods of 

 hyaline tissue, and at this time each rod is separated from its fellow by intervening 

 tissue. Each of the cartilaginous elements just described has its special muscular strand 

 on each side, and it is possible that they may at a later stage unite to form one javelin- 

 like neural spine. Further forward, indeed, the neural spine does develop as a single rod 

 of cartilage surmounted by a nodule of the same tissue which is trifid superiorly. In 

 Cottus quadricornis the neural spine in the mid-trunk region is cartilaginous, with one 

 superior (interspinous) element ; but the neural arch itself is formed by two dense 

 hyaline arms which grow out from the perichordal ring of the same tissue. In the post- 

 larval goby (Gobius ruthensparri) the interspinous element appears before any neural 

 arch or spine is developed, and it has the form of a rounded nodule at the summit of the 

 connective-tissue continuous with the perichordal sheath. In the young wrasse, ■£$ inch 

 in length, no supra-neural cartilage appears at all in the region of the dorsal fins. The 

 fin-rays are, as usual, formed by the union of paired hyaline rods, having a semilunar 

 form in transverse section — the concave surfaces being opposed, and the neural spine, as 

 will be described later, is formed of hyaline matter. 



On escaping from the egg the tail of Anarrhichas is more or less lobulated, though 

 in many it is lanceolate. A distinct constriction (PL XX. fig. l) occurs in front of the 

 organ, which then gradually widens out — the dilatation being more marked inferiorly 

 than superiorly. The notochord goes straight backward from the nuchal curve to the 

 commencement of the caudal region proper, and then tapers to the termination, the axis 

 of this part being in the same line as that in front, viz., horizontal. In many views, 

 in newly hatched forms (January), a slight fold appears at the margin of the caudal fin, 

 in a line continuous with the notochord ; but whether this is a definite structure or not 

 is uncertain. All that can be said is that the appearances indicated in the figure 

 (PL XX. fig. 1) were frequent, and recalled the notch above the tip of the notochord so 

 familiar in the larval salmon. Structurally the tail, at this stage, presents a minutely 

 cellulo-granular appearance (due to the cutaneous elements), most marked in the thicker 

 central region, and becoming translucent towards the margin. The embryonic fin-rays, 



* [It is with deep regret that the authors have just received intimation of the death of this experienced and meri- 

 torious worker in the field of Ichthyology — both British and foreign.] 



