834 PROFESSOR W. C. M‘INTOSH AND MR E. E. PRINCE ON 
but the abdomen is less tumid than in the last stage. Specimens slightly older than 
this are represented by Mr Coucn (Brit. Fishes, vol. iii. pl. eli. and p. 118) as 
THompson’s midge, and were referred by the late Dr Gray to the genus Coryphena, 
probably from the remarkable development of the ventrals. 
Specimens 24 mm. longer than the last described, viz, 12°5 mm. in length, show a 
large increase in the amount of black pigment on the dorsum, where it now gives rise 
to a mottled appearance, extending over the sides and tail. Only a few corpuscles exist 
near the ventral line behind the abdomen. The pectorals have increased in size and 
strength, whereas the ventrals, though still of extraordinary dimensions, are now only 
about one-fourth the length of the body, and are tipped with deep black, while the 
remainder (#) of each fin is very pale in colour. The sides are silvery almost to the base 
of the tail. In many of the specimens a parasite like a young Caligus projected from the 
branchiostegal region. The youngest examples of Motel/a above described occurred in 
32 fathoms water off the Isle of May, about 7 fathoms from the bottom, the others 
were obtained in the same region in 25 fathoms water and about the same distance from 
the bottom. 
When M. mustela reaches 24 or 25 mm. in length, the general silvery hue is marked, 
only the dorsum of the head and body being brownish. The five barbels are distinct, 
and the tips of the ventral fins do not project behind the pectorals, though their bases 
have now advanced considerably in front of the former. The eye remains comparatively 
large. The specimens of this size were obtained by the surface-net in Lochmaddy. 
At 29 or 30 mm. many of the adult characters have been assumed, the brownish- 
black pigment having spread over the upper lateral regions. The tips of the ventrals 
scarcely reach those of the pectorals, the three anterior rays being furnished with long 
sensitive tips. The abdomen and lower lateral regions are silvery. 
The older Motelle obtained are characterised, as Mr Day observes,* by their very 
bright silvery sides and dark bluish-black dorsum. The black axillary pigment occurs 
in most of these, but it varies in intensity. They range from 26 to 40 mm. That 
which most nearly resembles M. tricirrata possesses a pair of very short barbels or 
papillee in the premaxillary region, but sometimes one is indistinct, and they probably 
disappear during the subsequent stages. The ventrals extend about as far back as the 
tips of the pectorals, but their bases are considerably in front of the latter, the second 
ray being the longest of the three specially developed. All the black pigment has now 
disappeared. Contrasted with M. mustela of the same length, the eye is somewhat 
larger, and the space between them narrower, while the barbels are shorter. The first 
dorsal appears also to be somewhat shorter (from before backward). The free rays of this 
fin are characteristic in all the species. 
Two examples from the surface of the sea, south-east of the Isle of May, present 
only a single median barbel on the upper lip. Both show axillary black pigment, and 
in other respects correspond with the foregoing, except that the median barbel on the 
* Op. cit., p. 312. 
