THE LARGE-SPOTTED DOG-FISH. 
249 
for exclusion, but there was frequently one other in each oviduct at the upper 
end, or about to separate from the ovarium, one on each side. How long they 
are in passing along the oviduct, how often deposited, and how soon after de- 
position the young fish leaves his cell, are points unknown to me ; but I suspect, 
in reference to gaining his liberty, the young fish is rather in a hurry, for 1 have 
more than once taken very small spotted sharks swimming at large before the 
membranous bag of nutriment had been taken up into the abdomen, and before the 
young shark had begun to take food by the mouth. I will, however, send your 
sketch and queries to Mr. Couch.’ 
“ This gentleman replied : — 
‘ Polperro, Jan. 25, 1844. 
‘ Dear Sir, — I feel an impression that the figure of a ‘purse ’ which I re- 
ceived in your letter of the 24th December, is that of the large-spotted dog-fish, 
Scyllium Catulus. Both the British spotted dog-fishes certainly spawn twice 
in the year, as do many other species of fishes that are not commonly supposed 
to do so, a fact which I have ascertained by observation and dissection. But I 
have been somewhat unfortunate in reference to the larger-spotted dog-fish in 
not being able to obtain the ova of that fish directly from the body ; a circum- 
stance which arises from this fish going into deep water at the spawning time, 
when our fishermen do not find it convenient to follow them. I have obtained 
specimens, however, which I have been given to understand proceeded from this 
fish, and they very closely resemble the pencil drawing in size, form, and the 
raised ridge at the sides, and in the lengthened tendrils at the corners ; the co- 
lour a dark brown ; but I never saw any specimen with transverse plaits, which 
may throw doubt on the fact of its appropriation.* 
‘The ova of the Scyllia are deposited in pairs, an ovum descending at the 
same time to each corner of the uterus, but I am not able to say how many, 
constitute one laying, except that they are numerous. They certainly remain a 
considerable time before exclusion, a month or two at least, and perhaps more ; 
for the corals to which they have been attached, and especially the Gorgonice , 
are often seen growing luxuriantly round the tendrils in a manner to show that 
most of this growth must have taken place since the deposit. Sometimes also 
their surface is studded with small shell-fish, as Anomice and Pectens, of a size 
to render it probable that the time I have assigned to them may even have been 
exceeded. Jonathan Couch.’ 
“As, reasoning from analogy, I came to the conclusion that the ova must be 
those of S. Catulus, and as Mr. Couch has received similar ones which were 
stated to be the produce of this fish, I have thought it desirable to publish so 
much as we know of the subject, and to give a figure of the ovum, although 
actual proof is still wanting as to the species to which it appertains. Some of 
my queries to Mr. Yarrell bore on the subject noticed in the conclusion of Mr. 
Couch’s letter. Were it known how long the ova of the dog-fish were deposited 
before the young fish escaped, we could say that the adherent mollusca, zo- 
ophytes, &c., must have attained a certain growth within a limited period, but our 
information is not yet sufficiently positive on this head. The most newly de- 
posited ova under consideration were externally quite free from all parasitical 
growth, which was at first sight, or before they were opened, a good indication 
of their freshness. But whatever the time may be in which the ovum of the 
allied species, S. Canicula , is deposited before the exclusion of the fish, proof is 
afforded by one in my collection, containing a young dog-fish of this species all 
but ready for his escape, that before its birth would have taken place the Dis- 
copora hispida attached to the outside of its case had arrived at full maturity, f 
* As before mentioned, these plaits are not of specific value. — W. T. 
f Since the above was written, I have seen in the collection of Dr. It. Ball, 
Dublin, a similar case containing a young S. Canicula , on the exterior of which 
were groups of Lepralice of the full ordinary size, and two specimens of Serpula 
triquetra nearly an inch in length. 
