- 
— 
21 
other in form and structure, though not in colour, but differing from 
each other in their habits in a manner which had not been previously 
observed. I noticed that the ‘‘ picked dog” (A. vulgaris), swims 
about actively night and day, whilst on the contrary, the rough- 
hound /S. catulus), and the nursehound (S. canicula), are almost 
entirely nocturnal in their habits. During the day the first-named 
hug themselves close up to the surface of a rock, or, if possible, in 
some crevice, head up and stern down; and the latter lie on the ~ 
bottom, and remain motionless. It was known that one, the 
‘picked dog,” brings forth its young alive; and that the cther, 
the roughhound (and also the nursehound), deposits horny-cased 
eggs, which remain many weeks in the water, attached by tendrils 
to some sea-weed, stone, or Gorgonia, before they are hatched. 
But the method by which these eggs were made fast to their 
anchorage had never been seen by the eye of man, and naturalists 
differed in opinion whether they were intentionally fastened by the 
fish, or whether the tendrils were straight at the period of their 
extension and coiled around prominent substances by some “ in- 
herent vitality’’ of their own. I had the great pleasure of 
watching one of the oviparous dogfishes, the nursehound ( Scyllium 
canicula) deposit its pair of eggs, and of witnessing the manner 
in which the parent attaches them to plants, rocks, &c., at the 
sea-bottom, and I cannot better describe it than by quoting from 
my notes made at the time: At 1.15 one Sunday afternoon, 
one of the attendants at the Brighton Aquarium noticed that a 
nursehound had hanging from her, close to her body, an egg 
which had just been extruded. He quickly drew my attention to 
it, and I need not say how delighted I was to have the opportunity 
of observing an operation which has been a subject of speculation 
and conflicting opinion. The lady tested my patience severely, 
but it was ultimately well rewarded. The tank in which she was 
contains more than 50,000 gallons of water, and for five hours she 
swam round and about, generally near the surface, with an activity 
quite unusual to these fishes during the daylight, appearing neither 
to care for, nor to be incommoded by, the appended egg. But 
about half-past six p.m., when, as it afterwards appeared, the 
second egg was ready for expulsion, she began to rub herself 
heavily along the shingle at the bottom of the tank, and to 
‘endeavour to free herself of her incumbrance by vigorous con- 
tortions of the body and rapid muscular motion of the tail. In 
readiness for such an event, as we had no Gorgonias or Laminaria, 
I had previously ordered to be prepared some artificial Gorgonias, 
made of the twigs of a birch broom, and fastened firmly, in the 
shape of a little brush, to a heavy stone. One of these I now 
lowered into the tank, close to the parturient fish. For some time 
she took no notice of it, and continued, at intervals of about five 
minutes, her former meyements along the ground; but in about 
c 
