FISHES AND FISH DEVELOPMENT—PIERS. 99 
the fish itself and more pink, the darker shade arising from its 
contents. A brown tortuous line goes round the sack near its 
attachment to the fish, and bends downward at the anterior 
end. 
Total length from tip of snout to tip of tail about 4 em. 
Distance between the eyes (inter-orbital space), 7 mm. 
Head nearly one-fourth the total length. 
Breadth of head behind the eyes, 9 mm. 
Length and breadth of yelk-sack, 23 mm. 
Height of ditto, 18 mm. 
Length of maxillary barbels, 8 mm. 
: machin cs 4 mm. 
minkways' 1D. 17, 2, D.03 P. 1.6. V. 6. A. 19 (),C 16. 
This fish I have not been able to identify, the chief difference 
being in the great length of the adipose fin compared with its 
height. 
On referring to the eighteen fishes, whose development is 
treated of by Ryder, we find that the greatest length of time 
required for the absorption of the yelk is twenty days, which is 
the case in the Ictalwrus albidus or White Cat-fish. At this 
time the caudal is not yet perfectly developed. Our fish ap- 
pears, in the proportionate size and relation of the fish proper 
and yelk-sack, to correspond with the above when just hatched ° 
(sixth day). Yet on a closer examination the immense difference 
between their respective stages of development is at once 
observed. We find that while the J. albidus has no determinate 
fins whatever, but only a median fin-fold, our Cat-fish is perfect 
in every particular, and exhibits, in its accessory caudal rays 
and sharply defined adipose fin, evidences of its very advanced 
development. The latter fin, in regard to the White Cat-fish, is 
not perfect until about eighty days. 
Now this early development is very curious when we compare 
it with other fishes at an apparent similar age, and is evidently 
worthy of careful attention. 
