SECTIONAL TRANSACTIONS.— D. 371 



investigations upon herring scales suggest the possibility of predictions as to 

 the abundance or otherwise of the fish in particular years, in the absence of 

 any unforeseen disturbing fartoi-s. 



(c) Prof. Otto Pettersson. — On the Periodic Character of 



the Scandinavian Herring --fishery. 



Tlie essence of my paper is to draw attention to the great secular periodicity 

 in the movements and the circulation of oceanic waters and their influence on 

 the migrations of fishes (the herring) which have occurred in our parts of the 

 sea once in every century during the last thousand years. 



(rf) Mr. B. Storrow. — Herring Fhicttiationa. 



There is a relation between tidal phenomena and the productivity of the 

 herring-fishery of the East Coast of Scotland. Tidal phenomena precede herring 

 catches by four years, and the curves show, alternately, periods tending to 

 parallelism and convergency. Data for catches arranged in a nine-year period 

 show that the fourth year after the c;reatest tide-generating force exerted by 

 the moon (Pettersson) is marked by high catches. There is a period of 18-19 

 years in the catches of winter herrings off the East Coast of Scotland, and 

 probably in the East Anglian fishery. The poor quality of the herrings of 

 11920 and 1921 and the large numbers of young spawning fish in the shoals 

 were due, probably, to the same factors which determined the liver yield from, 

 and young fish amongst, Norwegian Skrei. It is probable that further work 

 will enable us to foretell some of the good summer fisheries. 



(e) Dr. Wm. Wall.^ce. — On the Spawning and Early Stages of 



the Herring in the North Sea (S.W.) and English Channel (E.). 



From the results so far obtained, it appears that spawning occurs chiefly 

 west of .3° E. long., and at places where the bottom deposit contains an 

 appreciably large proportion of stones and other coarse material. The period 

 of spawning varies with the latitude, thus : Off Northumberland in August 

 and September ; on and around the south part of the Dogger and off Whitby 

 in September and October ; off the Wash and Norfolk coast in October and 

 November ; in the southern termination of the North Sea and in the eastern 

 part of the English Channel from November to January. The post-larvse. 

 as they rise from the bottom and reach a certain size, are drifted towards the 

 shore on both sides of the North Sea. Erom observations made in the Wash, 

 Thames Estuary and adjacent waters, it appears that it may be possible to 

 distinguish adults of the more northern autumn-spawning herring from those 

 of the southern winter-spawning herring by the size of the area delimited by 

 the first winter ring in their scales. 



12. Mr. R. S. Clark. — Features in the Development of Rays and 

 Skates. 



The egg-capsules when deposited are buried in sand, and in most cases in 

 shallow water. There they undergo a period of incubation, rangin.g in the 

 different species from four to fifteen months. They are adapted to the life of 

 the embryo. At first they are filled with a thick plug of albumen, which soon 

 disappears or is absorbed, and then a constant stream of water passes through 

 the open slits on the horns, tlie aeration being assisted by the rhythmical move- 

 ment of the embryo. Tran.sitory branchial filaments, elongations of the gill 

 lamellae, which are absent in the spiracle, persist to the end of embryonic life 

 and are gradually absorbed with the development of the gill arches. Their 

 function appears highly respiratory, but they may help in absorption, as may 

 probably happen in the absorption of the albumen. Fertilisation of the egg 

 must be effected in tl;e upper reaches of the oviduct, and the subsequent passage 

 of the complete egg and capsule must be fairly rapid. A single copulation has 

 been found effective after a lapse of four months. The embryo becomes 

 oriented towards the lona: horn end of the capsule, through which it passes 

 head first at hatching. The yolk is withdrawn into nn internal yolk sac which 

 opens dii-ectly into the spiral valve. A considerable amount of yolk is retained 



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