26 On the Ova of the Large Spotted Dog-fish. 



cies 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 larg'jr spotted dog-fish in 

 not being able to obtain the ova of that fish directly from the body ; 

 a circumstance 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, the raised ridge at the 

 sides, and in the lengthened tendrils at the comers ; the colour 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 descend- 

 ing 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 nume- 

 rous. 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 Gorffonia, 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 de- 

 posited before the young fish escaped, we could say that the adherent 

 mollusca, zoophytes, &c. must have attained a certain growth within 

 a limited period, but our information is not yet sufiiciently positive 

 on this head. The most newly-deposited 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 its escape, that before its birth 

 would have taken place, the Discopora hispida attached to the out- 

 side 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 Mr. R. 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. 



