Dec. 9. 1SS6] 



NA TURE 



129 



burgh ; the Rev. A. M. Norman, D.C.L. of Durham ; 

 and Mr. Hahburton, of University College, London. 

 Though the Marine Laboratories at Tarbert and St. 

 Andrews admitted of several important inquiries being 

 initiated, the Board is still greatly hampered for want of 

 proper boats, and throughout the year the limited amount 

 of dredging and field-work done was rendered possible 

 by boats supplied by Prof. Ewart. It is to be hoped that 

 arrangements will be made by the Admiralty, which will 

 admit of the superintending vessels undertaking a com- 

 plete survey of the spawning-banks and assisting in 

 work of a like nature when required. A small steamer 

 has already been provided for trawling experiments and 

 other work on the east coast. At the Rothesay A(iuarium 

 the spawning of the cod was studied by Prof. Ewart and 

 Mr. I5rook, who generally confirmed the observations of 

 Sars, and gained further information as to the natural 

 and artificial fertilisation of the eggs, and their buoyancy 

 before and after fertilisation in difterent kinds of water. 

 The appendix contains part ii. of a paper by Mr. Brook 

 on the development of the herring. Experiments made 

 in artificial fertilisation of herring eggs appear to justify 

 the following conclusions : — 



(l) The ova retain their vitality, and are capable of 

 being fertilised from forty to forty-eight hours after the 

 female is dead. In the experiments performed, forty- 

 eight hours seems to be a little outside the limit at which 

 the eggs are capable of being fertilised, but it is probable 

 that temperature may have an influence on the vitality of 

 the ova. (2) The spermatozoa do not retain their vitality 

 for nearly so long a period. Three hours appears to be 

 the limit indicated by the above experiments. (3) The 

 egg capsule never separates from the yolk excepting 

 under the influence of spermatozoa. It would appear 

 that when the ova and spermatozoa have partly lost their 

 vitality a partial separation of the egg membrane from 

 the yolk may take place, although the ovum is not truly 

 fertilised. Experiments proved conclusively that tire egg 

 capsule is not permeable to water until after it has been 

 penetrated by spermatozoa. (4) The egg membrane is 

 covered with a viscous secretion when the ovum leaves 

 the oviduct, which serves for the attachment of the ovum. 

 This viscous layer gradually hardens in sea-water. Active 

 spermatozoa are able to penetrate this layer some hours 

 after it has set, but this power appears to be confined to 

 the first twenty-four hours after deposition. (5) There is 

 no collection of germinal protoplasm at the surface of the 

 yolk in the ripe ovarian ovum, nor is a germinal disk 

 ever found so long as an ovum remains unfertilised. The 

 formation of the germinal disk cannot be made out in 

 living ova, and its true nature can only be determined 

 from a study of sections. Investigations on the forma- 

 tion of the blastoderm, and examination of a large num- 

 ber of sections, lead to the conclusion that the animal 

 pole of the ovum gives rise to the ectoderm. In many 

 forms the animal pole at the time of the formation of the 

 segmentation cavity consists only of true archeblast 

 cells. In the herring, and probably some other forms, 

 the animal pole receives an addition of cells from the 

 parablast prior to the formation of the segmentation 

 cavity. The primitive hypoblast, which is almost entirely 

 derived from the parablast {i.e. from the vegetative pole), 

 gives rise to the mesoderm, and the secondary hypoblast 

 (endoderni) remains as a single row of cells in connection 

 with the parablast. 



If these conclusions are correct, the similarity between 

 the development of teleosteans and amphibians {Rand) 

 cannot fail to be noted. The derivatives of the animal 

 and vegetative poles are in both cases practically identical. 

 The secondary segmentation (budding) in the parablast 

 of teleosteans must then be regarded as the necessary 

 consequence of the relative distribution of protoplasm 

 and yolk in the vegetative pole. The primitive hypoblast, 

 as here described for the herring, is precisely homologous 



with that of Amphioxus. In both cases the primitive layer 

 gives rise to mesoderm, notochord, and true endoderni. 

 The position here brought forward is one advocated by 

 Mr. Brook over a year ago, but from the nature of the 

 material then at his disposal he failed to observe the 

 details of the process. Quite recently. Dr. Ruckert, who 

 has been studying the behaviour of the parablast in Elas- 

 mobranchs, has come to conclusions practically identical 

 with those here advocated for Teleosteans. 



The question, " Are herring ova likely to develop nor- 

 mally on the deep off-shore fishing-banks ?" is discussed 

 by Prof. Ewart in a way which shows that the Board 

 aims at practical results as much as mere scientific inves- 

 tigations. 



Until comparatively recent years nearly all the herring 

 taken in summer were captured by small boats within a 

 few miles from the shore, in 1852, e.g., immense herring 

 shoals reached the iVIoray Firth to spawn on the Guillam 

 and other in-shore banks. Since 1852 the fishing boats have 

 greatly increased in size, and owing to the introduction 

 of cotton nets, each boat has added greatly to its catching 

 power. 



As the boats have increased in size and sea-worthiness, 

 the fishermen have proceeded farther and farther to sea in 

 search of the herring shoals, and now the greater number 

 of the herring are taken from forty to sixty miles from the 

 coast. It is often alleged that it was owing to the herring 

 deserting the in-shore grounds that the fishermen proceeded 

 to sea in search of the shoals, and also that it is because the 

 fishermen disturb and break up the shoals early in the 

 season that they no longer or seldom visit their old 

 spawning-grounds. There is no doubt that during the 

 last fifteen years comparatively few herring have been 

 captured during the summer over the in-shore banks of 

 the Moray Firth ; but whether this is the result (as is 

 alleged) of the fishermen intercepting and breaking up 

 the shoals before they have had time to reach the in-shore 

 ground it is impossible to say. It is, however, a question 

 of great interest, and one which could in all probability 

 be easilv settled. If the fishermen were to refrain from 

 fishing for one year in the various districts along the east 

 coast until the fish had reached maturity, this problem 

 would most likely be solved. In all probability the herring 

 would be found as abundantly as in former years in the 

 in-shore waters, and the fish captured would be larger and 

 riper than those taken early in the fishing-season of 

 former years from the corresponding shoals. 



That the takes during recent years have consisted 

 chiefly of small fish (so-called maties), will be evident by 

 a reference to Reports of the Fishery Board. It is gene- 

 rally admitted that the great depression of the fishery 

 industry which now prevails would, to a great extent, have 

 been prevented if half of the small herring (the inaties) 

 had been left in the sea. Many of those who account 

 for fewer herring being captured in-shore, by saying it is 

 impossible for them to run the gauntlet of the thousands 

 of nets that are night after night drifting across their 

 path, assert that the eggs are incapable of developing in 

 deep water, and that in course of time the off-shore shoals 

 will diminish or disappear. Of this there is in the mean- 

 time no evidence. As a matter of fact, for all we know 

 there may have been immense shoals of herring spawning 

 on the banks which lie at a distance of from thirty to si.xty 

 miles off the Scottish coast for centuries. 



The existence and continuance of off-shore shoals will, 

 to a great extent, depend on whether the herring are able 

 to reproduce themselves without visiting the in-shore 

 spawning-banks, and the success of the herring industry 

 .will depend on whether the herring shoals, which are 

 invaded annually by our fishing fleet, continue to spawn 

 sufficiently near the coast to render their capture a pro- 

 fitable enterprise for our fishermen. For this it is 

 necessary to have large shoals moving in limited areas, 

 and these are only found on the east coast during the 



