Early Post-Larval Stage. 11 



on the body at the upper corner of the gill-opening. The borders of the fins have 

 a crenated appearance, but there are no signs of thread-like appendages. The 

 pelvic fins have grown greatly, and now extend beyond the mid-point of the larva, 

 but, in addition they have increased their surface enormously by the development 

 of subsidiary lobes. Scattered groups of delicate pigment appear on the pelvic 

 fins, but there are distinct pigment groups at the tips of the long rays. 



A specimen from Scottish waters of somewhat similar size is described by 

 Fulton (1902). The head is about one-quarter the length of the body, and it is more 

 than a third deeper than long ; in a front view, th e breadth of the head is about 

 seven-tenths of the height. Fulton also describes the movements in the water 

 of the pelagic form at this stage. " The little post-larval Angler, about 10 mm. 

 long, has a very odd appearance as it swims through the water by the rapid vibration 

 of the pectorals and tail, the long black verticals projecting downwards and upwards 

 and quiescent below, and the almost equally long, black-tipped rays of the first 

 dorsal standing erect on the top of the head. The eyes are large, deep ultramarine 

 in colour, and look upwards and forwards, and the mouth is usually gaping, each 

 jaw being provided with a row of ten or tv/elve minute- pointed teeth. They were 

 observed to dart and snap at particles in the water." 



Five Distinct Rays in the First Dorsal Fin, the Elements of the Second 

 Dorsal and Anal Fins Complete. 



{Fig. 7). 



As the post-larval form grows, there is a progressive development of all 

 the different parts. The head and body become longer and more massive in 

 comparison to the total length of the larva. The fins are also progressively devel- 

 oped, and, at the stage illustrated in Figure 7, there are now five distinct rays 

 in the first dorsal fin, whilst the elements of the second dorsal and anal fins are 

 complete, and the caudal fin has also appeared. The total length of a post-larval 

 form at this stage is about 15 mm. when preserved in formalin, and the distance 

 from the tip of the lower jaw to the anus 5^2 mm. In the specimen figured, the 

 mouth is widely open with the lower jaw the more prominent, and minute conical 

 teeth and papillae denoting the positions of future teeth can be seen in both jaws. 

 The eyes are now somewhat higher in the head, gradually tending to look upwards 

 as well as outwards. The horizontal diameter of the eye is one fourth of the length 

 of the body from the tip of the snout to the anus. The anterior margin of the eye 

 is slightly more than half its horizontal diameter from the anterior margin of the 

 head. The gill openings are large and distinct, and the bases of the pectoral fins 

 are inserted on the body almost in a line with the eye at the upper angles of the 

 gill-openings. Both pectoral and pelvic fins are extremely well-developed. The 

 base of the pectoral fin is kidney-shaped. The membranous fan-shaped portion, 

 mth fin-ray supports quite distinct, is very large. When fully expanded, the 

 pectoral fin covers the bases of the two posterior rays of the first dorsal fin, and 

 also the anterior rays of the second dorsal and anal fins. There are no traces of 

 filamentous prolongations of the rays. The pelvic fins, inserted on the ventral 

 surface of the head, anterior to the pectoral fins, have an extensive surface. The 

 longest ray extends behind the second dorsal and anal fins, but the surface is in- 

 creased by the development of secondary lobes. These fins are dehcately pigmented 

 along the rays, and the pigment is most intense at the tips of the rays. There are 

 five distinct rays in the first dorsal fin, the tips of which end in long filamentous 

 processes. The bases of the rays are enveloped in the same membranous sheath 

 which extends some distance up the posterior four rays. In front of the first 

 ray, the rudiment of a sixth ray has been formed, the tip of which has just made 

 its appearance in a depression above the contour of the head. The interspinous 

 elements of the second dorsal and anal fins are now well-formed, and eleven dorsal 

 and nine anal rays can be counted extending to the edge of the embryonic fin. 

 The embryonic fin, however, is still complete, and extends beyond the tip of the 

 still straight notochord. The rays of the caudal fin are much better developed 

 on the ventral side of the notochord some distance from the tip, but the basal 

 elements of the caudal fin are not yet distinct from each other. 



