764 Proceedings of the Boyal Society 
the body. The newly- hatched larva is 3 mm. in length. A larva 
with these characteristics is described by Von Hensen in the fourth 
Eeport of the Commission zur Untersuchung der Deutschen 
Meere in Kiel, part ii. ; the species is there also left undetermined. 
The relation of the ventral median fin to the anus is not discussed 
by Von Hensen. This relation is as follows, and is shown in the 
woodcut. The median fin extends continuously along the median 
dorsal line round the end of the tail to the anus, and passes 
continuously from thence to the yolk-sac, having about the same 
breadth throughout. There is no break in the fin at the anus, as 
the latter opens on the edge of the fin, the terminal portion of the 
intestine projecting downwards from the trunk. 
There is at least one other Teleostean larva in which the prim- 
ordial median fin has exactly the same relations to the anus and 
yolk-sac as in the larva just described. This second case is that of 
the herring. The existence of a pre-anal portion of the median 
ventral fin in the herring larva was pointed out by Dr C. Kupfier* 
in 1878, but he includes it in his general description, laying no 
particular stress on it.f Balfour, in his Corny. Embryology, 
although he refers to Kupffer’s work, has overlooked this fact in 
the structure of the herring larva, making the general statement 
that in the young Teleostean the ventral fold of the median fin 
ends anteriority at the anus. 
It is uncertain whether there are other Teleostean larvae in which 
the same state of matters obtains, and I do not know at present 
what relation the development of the pelvic fins bears to the 
ventral median fold in the two cases mentioned. On the two 
occasions, when I had the undetermined larvae above described 
in the laboratory, I was unable to keep any alive for more than six 
days after hatching. At the end of that time the pre-anal ventral 
fin was still unchanged, and no trace of pelvic fins could be seen, 
* Laichen u. EntwicTclung des Ostsee Herings, Berlin, 1878. 
t Having carefully studied the development of the herring in the month of 
August, 1 can fully confirm Kupffer’s description of the newly-hatched larva. 
The proportion of the length of the body through which the pre-anal ventral 
fin extends is considerable, the whole length of the larva being 5 *2 mm. , while 
the length of the pre-anal fin is 2 ’5 mm. The larva of the herring is closely 
similar to the first larva described above ; it is quite transparent ; the yolk 
consists of separate spherules, and the notochord has but one column of cells. 
{Note added Sept. 19, 1884.) 
