76 



NA TURE 



[December 24, 1891 



theory of Weismannism minus natural selection. In the second 

 place, we believe that Wei^mann means permutations, though 

 he uses the term combinations. After a football team has been 

 selected, the men can be arranged in|ii different ways. The 

 arrangements would virtually constitute~new teams, and news- 

 papers would speak of them as strong and weak combinations. 

 The combinations of the Ahnenpiasmas can be assumed to be of 

 a similar kind. The arrangement almost certainly counts for 

 something. Nevertheless, Prof. Hartog's contention— that the 

 elimination of Ahnenpiasmas in the shuffling process would lead 

 to ever-increasing simplicity— demands serious consideration, for 

 duplication lessens the possible number of permutations and 

 combinations. I would point out that we may conceive that 

 the Ahnenpiasmas were, in asexual unicellular organisms, either 

 all the safne, all differetit, or in intermediate conditions. In 

 any one of these cases we must assume that m, the number of 

 individuals, was much greater than «, the number of 

 Ahnenpiasmas present in every individual. With the evolution 

 of sexuality (all the individuals being different) we should get 

 combinations of, at least, m Ahnenpiasmas taken « at a time. 

 Different permutations of the same combination would be, of 

 course, possible, giving rise to other combinations, using the 

 word in the general sense. We must suppose that natural 

 selection operated upon the variations produced by these first 

 c )mbinations. Natural selection had operated upon the uni- 

 sexual ancestors of these sexual forms. We can at least conceive 

 that development would follow one of two courses. Along the 

 first, combinations in which more than one unit of a kind ap- 

 peared would, if possible, be prevented. Such might arise, but 

 under the operation of natural selection they would not be allowed 

 to perpetuate themselves. Along the second, such combinations 

 might arise and be perpetuated. In either case, it must be 

 assumed that the combinations which survived were such as were 

 best adapted to the varied combinations of external conditions. 

 This may be made clearer by an illustration. In Rugby foot- 

 ball, combinati >ns of 15 in which 8 or 9 of the men— the 

 forwards— are all the same would be strong, whereas, if all were 

 different, they would he weak. In Association football, strong 

 combinations could only be made up by selecting different types 

 of players for the different places. I am inclined to believe that 

 both cases are followed by Nature. The one which I have 

 illustrated with reference to Rugby football cannot, however, 

 have been generally followed. It is an adaptation for which the 

 organism has ultimately to pay dearly, and is as dangerous to 

 the development of the ///;>'/mot, as we may suppose parthenogenesis 

 to be to the species. Taking the case of plants, I would say that 

 the one course may have been followed along the line of de- 

 velopment of the main archegoniate series, the other in the 

 development of such divergent groups as the Ustilagineee and 

 Gastromycetes. The argument of Prof. Hartog, therefore, while 

 of no avail as directed against Weismannism, is of use in so far 

 as it enables us to better understand divergence I am inclined 

 to think that it may serve also to explain the remarkable per- 

 sistence of such forms as Nautilus. It suggests, too, an explana- 

 tion of the disadvantage of breeding " in and-in." Finally, I 

 would remind Prof. Hartog that neither of the disciples of 

 Weismann apparently believes in the non-variability of the 

 Ahnenpiasmas. If their beliefs have a substantial foundation, 

 it follows that the number of possible combinations becomes 

 absolutely unthinkable. 



I shall be much obliged to Prof. Hartog if he can inform me 

 of any theory of heredity whose foundations are not " more or 

 less mythical." There are, no doubt, many difficulties in Weis- 

 mannism, before one of which, the theory, having served its 

 time, may come to the ground. I do not think that Prof. 

 Hartog's is one of them. A. H. Trow. 



Penarth, Cardiff, December 10. 



Destruction of Immature Sea Fish. 

 In your number of November 19 (p. 49) you review the Ninth 

 Annual Report of the Scotch Fishery Board. I have not seen 

 the Report, but assume that your reviewer's statements as to its 

 contents are correct. My object in writing is to draw attention 

 to the opinions attributed to Dr. T. Wemyss Fulton as to the 

 destruction of young fish by shrimpers. I may say at once that 

 I am one of the "very many" to whom the "results" are "sur- 

 prising " as your reviewer remarks. I am an old shrimp-trawler 

 in the Dee and along the Flintshire coast, and I have no hesita- 

 tion in saying that, as regards the Dee and, I believe, the 



NO. I I 56, VOL. 45] 



Mersey and the Lancashire coast as far north as the Ribble, the 

 destruction of young fish is absurdly under-estimated, whether 

 I judge by my own experience or by that of Mr. R. L. Ascroft, 

 of Lytham, with whom I have been in correspondence on the 

 subject since 1889. This gentleman, however, informs me that 

 Dr. Fulton's information was obtained from Morecambe Bay, 

 where smaller trawls are used, and the boats drift with the tide 

 instead of sailing. Dr. Fulton has been informed that in the 

 Sol way Firth a single boat in one year captures over 1 10,000 

 immature plaice. If the word "year" is not a mistake for 

 "week," either the statement is immensely under-estimated or 

 the conditions in the Sol way must be very different from what 

 they are further south. This may be judged by the following 

 extract from a letter written by Mr. Ascroft in 1889. I may 

 say that this gentleman (who is now, I am glad to say, a mem- 

 ber of the Lancashire Fishery Committee) has had a long and 

 practical experience in all kinds of sea-fishing on the Lancashire 

 coast, and is a careful and accurate observer. He writes as 

 follows : — " Shrimping destroys more young fish than almost 

 any other agency. I have seen in Formby Channel locwt. of 

 young flukes destroyed, not one the size of half-a- crown, by one 

 boat, and there were sixty boats there that day." 



Now, taking the weight of a fluke the size of half-a-crown at 

 4oz., a simple calculation will show that each boat captured 

 35,840 young flukes (a term which includes plaice and dabs) in 

 one day, or 215,040 in a week of six days — nearly twice as 

 many as Dr. Fulton's figures for a year ! And elsewhere Mr. 

 Ascroft says : " You may put it as an axiom that 90 per cent, 

 of fish that comes on a boat is destroyed, as when trawling they 

 sail back as they have got their net, and do not commence 

 sorting the take until the net is out again, and they do not, in 

 shallow water, throw the rubbish" {le. everything except 

 shrimps) " over until they turn out to haul, for fear of getting it 

 into the net again." All of which I may say is borne out by my 

 own experience. 



The following is an extract from my diary, written July 10, 

 1885, when Fishery Committees were not dreamt of. The 

 occasion was an excursion for dredging purposes of the Chester 

 Society of Natural Science, when I took my boat and trawl to 

 meet their steamer at the mouth of the Dee. The Green Buoy 

 marks the bar near Prestatyn, and I let down the trawl in mid- 

 channel (about 5 fathoms) in the hope of getting some natural 

 history specimens :—" Began to trawl just below the Green 

 Buoy. Got a few goodish soles, and an immense number of 

 young soles, which always squeeze their heads through the meshes. 

 ( IV. B.— Shrimp-trawling at this time of year should only be allowed 

 within a quarter of a mile of the shore, to avoid the immense 

 destruction of fry, which mostly lie further out.) Afterwards 

 got a good haul of shrimps as close in (shore) as we could go." 

 I have a perfect recollection of the occasion, and although 

 the trawl was only down about twenty minutes I was horrified 

 at the number of young soles which were in the net, and most 

 of which had choked themselves. But there were very few 

 shrimps, which mostly lie in very shallow water near the edge 

 of a sand-bank. 



As a remedy for this destruction I would suggest that the 

 principal breeding-grounds be ascertained, and trawling on them 

 prohibited at such times as the young fish are there. If the 

 prohibition be evaded, then a steamer-load of very large angular 

 stones, distributed from 100 to 200 yards apart on the selected 

 grounds, would effectually prevent trawling, and at the same 

 time, as they became covered with weed, afford shelter and 

 food to the fish and shrimps. This has been done by Nature in 

 this bay, where large boulders washed out of the drift that here 

 forms the coast-line strew the shore at wide intervals, and 

 render trawling for shrimps impossible, though hand nets can 

 be and are worked. 



I trust the importance of the subject will excuse the length 

 of this letter. Alfred O. Walker. 



Nant y Glyn, Colwyn Bay, December 14. 



The Salts in Natural Waters. 

 The inquiry of your correspondent " R. B. H.," in Nature 

 of November 26 (p. 78), may be answered as follows. In the 

 analysis of an ordinary water, after determining the respective 

 amounts of lime, magnesia, (soda), carbonic acid (combined), sul- 

 phuric acid, nitric acid, and chlorides (these being the constituents 

 met with usually in such a water), we proceed to combine the acids 

 and bases thus : the carbonic acid is calculated to carbonate of 



