DEVELOPMENT AND LIFE-HISTORIES OF TELEOSTEAN FISHES. 833 



There is no uncertainty, however, with regard to the genus of the form about to be 

 described. It is clearly a Motella, though more probably M. tricirrata than M. 

 mustela. 



The youngest stage captured in the large mid-water net at the end of August is 

 6 mm. in length (PI. XVIII. fig. 6), and the embryonic fin (ef) is still connected with 

 the base of the tail both dorsally and ventrally, the specimen being apparently about 

 the stage of Agassiz's, pi. vii. fig. 6. The body of the British fish is, however, 

 proportionally shorter and deeper. The head is large and the snout blunt, the high 

 arch formed by the gape being noteworthy. The mandible is large, prominent, and 

 protrudes somewhat in front of the snout. The hyoidean region is well developed, 

 though the branchiostegals are indistinct. The abdomen (abd) is very prominent and 

 large, and has a silvery iridescent sheen superiorly. A trace of the choroidal fissure 

 persists beneath each eye. Numerous blackish pigment-corpuscles occur over the 

 brain; but only an interrupted line extends along each side of the anterior half of the 

 dorsal fin. The pectorals (pj) form large fan-shaped structures directed upward, and 

 the ventrals (vf), which are blackish in hue, are of great size ; but instead of arising 

 considerably in front of the pectorals, as in the adult, they spring by a pale base only 

 a very short distance in front of the pectorals. These long black fins are about one- 

 third the length of the fish, and when first seen with the naked eye they resembled a 

 pair of powerful black spines, for the protection of the tumid abdomen. Four of the 

 rays, as in the American form, are largely developed. The body is of a general pale or 

 slightly silvery hue in the preparation studied, and the stomach contained minute 

 copepods. A somewhat silvery form, only 2 mm. longer (viz., 8 mm.), shows the dorsal 

 and anal fins almost separated from the tail. The head is now better developed, and 

 the delicate branchiostegals are very evident. The pigment over the brain is very dark, 

 and a dotted band proceeds from this region backward for some distance on each side 

 of the middle line. A group of pigment-specks also occurs laterally below the posterior 

 part of the dorsal fin. From the elongation of the body, the ventrals do not seem to 

 be so long. This example was procured on the 21st July at 22 fathoms, but the same 

 stage has been seen at the surface. In young forms, apparently pertaining to Motella 

 mustela, the dark ventrals show dull yellowish rays. 



The next stage (PI. XVIII. fig. 5) reaches a length of 10 mm., and the examples seem- 

 ingly belong to the same species. A silvery hue predominates over the cheeks, abdomen , 

 and partially on the posterior region of the trunk. Over the brain and along the dorso- 

 lateral line the black pigment is more abundant, while a blackish spot occurs a short 

 distance in front of the tail. The continuity of the dorsal (df) and caudal fin (cf) is 

 less prominent though still present, and the tail is more elongated — tapering slightly 

 towards the tip. The arch of the mouth is still high, though the forward growth of the 

 premaxillary region renders it less conspicuous. The black coloration of the ventrals (vf) 

 is confined to rather less than the distal half of each fin, and the length of these organs 

 is proportionally shorter in relation to the body of the fish. * The eyes are really larger ; 



VOL. XXXV. PART III. (NO. 19.) 6 O 



