NOTES ON TRLEOSTEAN OVA AND LA71VAE. 3 



The ova and larvae of the majority of species occurring here are 

 alrea<ly more or less completely known, thanks to the labours of 

 Cunningham, Holt, Mcintosh, Masterman, etc., in this country, and 

 to Ehrenbaum and other continental investigators, so that the main 

 object of the descriptive notes which follow is to fill up gaps or to 

 amplify those previous observations which still lack completeness. It 

 is, perliaps, unnecessary to point out that records of such essential 

 diagnostic characters as dimensions, additional to those which have 

 been made on an extensive scale in investigations made in various 

 parts of the North Sea and elsewhere, are of no little importance and 

 value, owing to the local variation wdiich occurs in such respects. 



In glancing at the general constitution of my egg samples, as shown 

 in Table I, perhaps the most striking feature is the vast preponderance 

 of those belonging to unmarketable forms. The species which afibrded 

 the most numerous pelagic eggs was the rockling, Onos (Muiella) mvstela, 

 and not far behind this in abundance come the gold-sinny or rock- 

 wrasse (Ctenolahrus rupestriy^, the boar-fish (Capro's aper), and the 

 dragonet {Callionymus lyra). Doubtless more eggs of such important 

 families as the Gadidae and Pleuronectidae would have been taken if 

 more ofi*-shore collections had been possible. One may assume that 

 the relative abundance of planktonic eggs, if sufficiently numerous 

 samples are taken, is a fairly reliable index to the proportionate 

 numbers of mature fish occurring in the area under observation at the 

 spawning period. It is therefore to be expected that samples of 

 planktonic eggs from inshore areas should consist predominantly of 

 those from the littoral species of rockling and wrasse.* The same 

 cause, however, does not explain the predominance of dragonets, boar- 

 fish, and Norwegian top-knot over such forms as whiting, dab, plaice, 

 and sole, which are marketable fish of much importance to our local 

 trawlers and line fishermen. The general aspect of the case is that 

 species which are regular objects of the trawlers' pursuit are poorly 

 represented in our egg samples. How far trawling itself is responsible 

 for this condition of things is an open question, which in any case 

 it is not in my province to attempt to answer here. But it is a note- 

 worthy fact that the forms mentioned above are of such small size 

 that they would to a great extent escape through the meshes of an 

 ordinary trawl, and therefore stand the best chance of surviving on a 

 well-fished ground. The result cannot be entirely attributed to local 

 distribution of the mature fish, for tlie Norwegian top-knot has practi- 

 cally the same distribution here as the sole, thickback, *' merry-sole," 



* It should be rcnieirihcred that only one species out of the four Plymouth wrasses (viz. 

 Ctenolahrus ■nqjestris) produces pelagic eggs. 



