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SCIENCE-GOSSIP. 



owing to their lightness and the absence of porosity 

 in their tests. The period of flotation will con- 

 sequently be found to vary greatly with different 

 forms ; for while many Foraminifera sink within a 

 few minutes, and the greater number within twenty- 

 four hours, there are others which are capable 

 of resisting a prolonged immersion in water. In 

 experiments that I made some years ago, I found 

 a few Lagenae and Miliolinae still floating at the 

 expiration of a fortnight, during which about ninety- 

 nine per cent, of the originally floating Foraminifera 

 had gradually filled and sunk. As a general rule 

 muddy gatherings yield more floatings than sandy 

 ones, and the Foraminifera float for a longer period. 

 This is doubtless due to the preservative effect 

 of the mud upon the sarcode body of the animal, 

 which, filling the foramina, prevents the ingress 

 of the water. 



The method of washing the Foraminifera, etc., 

 out of the sand by " rocking " the material under 

 water, as described by Dr. Bryan, is very useful, 

 and may be carried out with the material which 

 remains after the withdrawal of the floating 

 forams. I have found a half-plate size photograph 

 developing-dish the most useful piece of apparatus 

 for the purpose. By careful manipulation it is 

 possible after rocking the Foraminifera into a pile 

 in the corner of the dish, to pour them out into a 

 wire sieve with a very small admixture of sand. 

 If desired, the contents of the sieve can be rocked 

 a second time and the sand entirely eliminated. 

 The great drawback to the method is the fact that 

 all objects of less specific gravity than the quartz 

 sand come to the top under the rocking action of 

 the water. Hence we find that the contents of the 

 sieve include a large percentage of miscellaneous 

 organic debris, especially in the case of shore 

 gatherings or dredgings from shallow water near 

 a coast line. The principal foreign ingredients 

 are : (a) vegetable and animal debris, chiefly the 

 woody fibres of vegetable tissues, fragments of 

 algae, the insoluble residue of sewage, etc. ; (b) 

 coal and coke dust derived from the ashes thrown 

 overboard from steamers ; I have seen gatherings 

 which were almost uniformly black from the large 

 percentage of carbon contained in them ; (c) Ostra- 

 coda, bryozoan and molluscan fragments, etc. 

 The last may be disregarded as unavoidable and 

 not objectionable ; but the removal of the coke dust 

 and vegetable debris must be effected, at any rate 

 partially, and the task is a most difficult one. In 

 fact I have not as yet succeeded in devising any 

 method of separating them without at the same 

 time losing a considerable percentage of the 

 Foraminifera in the process. A large amount of 

 the organic debris can be dissolved by the 

 action of caustic potash, but much of it resists 

 the prolonged reaction, and even boiling, in this 

 solvent. The coal and coke particles, though 



equally objectionable, are of less frequent occur- 

 rence, being principally confined to shore gatherings 

 made in the vicinity of ports and steamer routes, 

 especially in the English Channel. Repeated 

 rockings will eliminate them to a considerable 

 extent, but owing to their size and specific gravity 

 being approximately the same as those of many 

 Foraminifera, neither rocking nor sifting will entirely 

 remove them from a gathering. 



The rolling method of separation mentioned by 

 Dr. Bryan is invaluable for certain purposes ; but as 

 a method of separating organic debris from the 

 washings, it can only be successful at the expense 

 of sacrificing the bulk of those genera which, 

 being more or less flattened in shape, will not roll 

 off the card, For instance, Cornuspira, Ammodiscus, 

 Spirillina, Planorbulina, and many other genera are 

 flat on both sides, and will remain in position 

 on a card tilted to quite a high angle, and long 

 after much of the organic debris has rolled off. In 

 fact I have found this rolling process a quick and 

 easy method of obtaining specimens of these and 

 similar species from gatherings known to contain 

 them. The same method may be employed to 

 obtain specimens of those more or less spheroidal 

 forams which commence to roll off the card as soon 

 as it is slightly tilted. 



In the "Journal of the Queckett Microscopical 

 Club " for November, 1897, W *H be found a paper 

 on " The Preparation of Foraminiferous Material " 

 in which I embodied the methods I have found 

 most useful ; and those of your readers who are 

 interested in the subject, but have no practical 

 experience, will, I think, find ample instruction in 

 my remarks. 



28, Glenwood Road, Cat/ord, S.E. 



Variations and Migrations of Mackerel. — 

 An important paper by Mr. Walter Garstang, 

 M.A., F.Z.S., the naturalist in charge of the 

 Fishery Investigations of the Marine Biological 

 Association, appears in the last number of the 

 journal of that Association, issued in November. 

 It occupies sixty pages, and deals most exhaus- 

 tively with the racial differences of Scomber scomber. 

 The American form of this fish differs very con- 

 siderably from those found in European waters ; 

 but, though constituting distinct varieties or races, 

 there is no reason to doubt their specific identity. 

 The establishment of geographical or local races 

 of mackerel settle several disputed points con- 

 cerning the migration of this fish. It is proved 

 that the mackerel does not make long migrations, 

 as once thought. Neither does it cross the 

 Atlantic. There seems to be little doubt that the 

 varieties found in the Irish seas do not wander in 

 winter far from their summer haunts. The North 

 Sea fish of this species appear to winter in the 

 English Channel, returning northward in spring. 



