OCCUREING IN THE NEIGHBOURHOOD OF PLYMOUTH. 47 



terminating before reaching the edge of the primordial fin^ shows 

 that the larva is one of the cod family. The hake^ Merliiccvus 

 vulgaris, has been found to have a single oil-globule, but the present 

 ovum has a diameter of '78 mm., that of the hake is larger, "94 to 

 1'0'S mm. Motella tricirrata has, according to Raffaele, an ovum 

 measuring '74 mm., while the ovum of Motella mustela, according to 

 George Brook (Journ. Linn. Soc, 1884), measures "65 to '73 mm. 

 Another feature characteristic of Motella and present in the ovum 

 under consideration is the presence in the earliest stage of several 

 oil-globules which afterwards fuse into one. This ovum was obtained 

 in considerable numbers to the east of Penlee Point on January 28th 

 and 30th, 1888. Some of those taken on the latter date hatched on 

 February 2nd. The length of the larva was 1'98 mm., and it had 

 black pigment only which was confined to the body of the fish, and 

 absent from the fin and the yolk-sac. It is not unlikely that these 

 ova really are those of Motella tricirrata ; the difference between 

 their size and that given by Raffaele is very slight. On May 31st 

 I obtained in the tow-net two specimens of a young fish 17 mm. 

 long, which agrees with descriptions given of the young Motella 

 tricirrata. The chief characteristic of this young fish (fig. 39) is 

 the great length of the ventral fins which extend back to the anus, 

 and the intense black colour of their terminal third. Another 

 curious point is that the caudal fin, although it has apparently 

 attained its final form, is almost completely homocercal, being sup- 

 ported by fin rays which have a symmetrical relation to about eight 

 terminal vertebree. The sides of these little fish had a very bright 

 silvery glitter. There was a small barbel on the symphysis of the 

 lower jaw. This young fish is identical with that described by 

 Couch (vol. iii, p. 113) as Thompson's Midge, which together with 

 the CoucMa argentata of Giinther (Catalogue, vol. iv, p. 363), is 

 identified by Day as the young of the three-bearded rockling 

 Motella tricirrata. Agassiz (Young Stages of Osseous Fishes, pt. 3) 

 describes stages of a young fish very similar to the one I have 

 described, and identifies it as Motella argentea, Rhein., but I do 

 not know if this species is the same as Motella tricirrata. The 

 young of Motella mustela, the five-bearded rockling, is known as 

 the mackerel midge, which has already five barbels, but its younger 

 stages may well be indistinguishable from those of Motella tricirrata. 

 These young Motella are said to form the principal food of the 

 mackerel in May, but I have not verified this at Plymouth. 



I found one specimen of hake perfectly ripe on July 6th, so that 

 this species spawns at Plymouth in summer ; Raffaele found it 

 spawning at Naples in May. 



I have taken other kinds of ova in the tow-net, but have not been 



