870 PROFESSOR W. C. M'IINTOSH AND MR E. E. PRINCE ON 
has still the embryonic fin, and the adjacent part of the dorsal fin is long. The fin-rays 
proper (inferior) are well marked and long ; and the outline of the tail is thus peculiar. 
The specimen, though apparently younger than the last stage figured by ALEX. AGassiz 
(op. cit., pl. xvii. fig. 2), if the condition of the tail be a reliable point, yet diverges 
very much from it: still more does it diverge from the older stages of GUNTHER and Day. 
The head forms an expanded flattened plate, rounded in front from the marked 
premaxillary curve, and with a median notch; while behind le the two nostrils, a little 
distance on each side of the middle line. The large eyes are situated more than their 
diameter behind the anterior margin of the snout, and less than four (about three and a 
half) of them would give the greatest transverse diameter of the snout. They are thus 
large and prominent, and look directly upward. The cranial and other cartilages have a 
covering of transparent hyaline bony tissue. Behind the eyes the body narrows to a 
slender region, which is barely twice the length of the head. This region still carries 
the embryonic fin dorsally and ventrally as a nearly uniform fringe, with the true 
fin-rays developing in it, though in the anal portion (ventral border) the marginal fin 
here and there retains its original condition. The other fins present in the specimen are 
a pair of enormous pectorals attached to the great shoulder-girdle, a plate passing 
transversely behind the branchiz. The ventrals are situated in the middle line just at 
the anterior end of the pectorals, but both the former are injured. They are very short, 
but the rays seem to have been broken; yet, allowing for this, they appear to be little 
developed. The anterior fold of the pectorals runs in front of these fins externally. 
The great changes that must ensue during development in regard to the gill-slits and the 
situation of the pectorals are noteworthy, while the ventrals remain almost in the same 
position. The under surface of the head is marked by the expanded hyoidean apparatus 
and the slender mandibular bars, the symphysis of the latter forming a sharp angle in 
the preparation. The gills are three in number, and the gill-slit is large and long, 
extending from the dorsal margin to the anterior ventral attachment of the branchiz. 
The branchiz have simple papillose processes. In the stomach were small Copepoda and 
larval Crustaceans. 
XII. Generat Remarks on Post-Larvau FIsHEs. 
Variability in the size of young marine fishes of the same season is one of the most 
conspicuous features in their history, and probably depends on the earlier or later period 
at which spawning takes place. Moreover, it is evident that in those species spawning 
by degrees considerable differences in size will occur, in the same fish, between the 
products of those ova shed first and those which issue last. Some species, for example 
the cod and the sole, seem to have annually a very extended spawning season, the sole 
commencing in May off the east coast, and continuing till August. The fact just 
mentioned is demonstrated in a single sweep of the mid-water net on suitable ground in 
