15 
season were deposited on the 14th of January, and during the 
- following week many others were successively attached to oysters 
on the sham gorgonias made of birch broom twigs, and fastened to 
_ heavy stones, which I placed in the tank for the use of the fish in 
_ their mooring operations. After that more than 200 of these eggs 
of the ‘ rough hound ” and many of the ‘‘nurse-hound”’ were laid 
in the Aquarium, and of the greater number of the former the date 
of deposit has been carefully noted. The finding of these eggs 
occasionally in the dredge, or cast ashore with the young embryo 
not half-grown in them, and yet having the outer surface of their 
shells covered with algce, sponges, and other marine organisms, in 
- acondition which indicated the growth of many weeks, had quite 
_ prepared us for watching patiently for some months for their 
arrival at maturity. For. the purposes of observation, I attached 
several of their eggs artificially to my sham gorgonias, and placed 
5. them where they could be conveniently watched. In some of these 
the movements of the young fish were clearly seen from its first 
7 existence as a minute, worm-like creature living apart from, but 
connected with the yelk-bag from which it derives its sole nutri- 
_ ment while in the egg. At the end of six weeks, the little fish is 
_ about an inch long, and attached by an umbilical cord or tube to 
the yelk-like sac or nutrient vesicle ; the head is of the ungainly 
shape usual in the embryonic condition of young fishes, the eyes 
disproportionately large, the ventral fins scarcely perceptible, and 
the tail and hinder portion of the body much elongated. For the 
first three or four months the young fish increases in size very 
owly, but at the end of that period its body is as long as the egg- 
se in which it is curled round. The contents of the umbilical 
sac or yelk-bag are gradually absorbed, and this appendage itself 
di minishes in size, so that a little more space becomes available for 
the youngster’s movements. But when it begins to be incon- 
‘yeniently cramped for room, it kicks out with its tail against the 
rounded end of the case (that which first issued from the ovaries) 
t 
with a steady, sustained stroke of thirty to the minute, something 
up ina boat, with his face to the bow, and pushing the sculls, 
i stead of sitting down and pulling them. The now hardened 
es of the wedge-shaped head, driven instinctively with 
emitting and regularly-delivered blows, like a mechanically- 
ked battering ram, split the two layers of the borny mem- 
ne of the case at its square end, and at length it forces a 
munication with the outside water, some of which enters the 
. The respiratory organs at this period are still totally different 
n those which will be of service to the young animal in its perfect 
n, and exhibit, with remarkable distinctness, the progressive 
es which these organs undergo in the fcetus of all vertebrate 
s. Instead of the gills, characteristic of the fish, it is fur- 
