THE HUXLEY FILE
[657] Some little time ago an eminent geologist, Professor Gumbel of Munich, applied to Sir Roderick Murchison for specimens of the Deep-sea Soundings which have lately been the subject of so much discussion. Sir Roderick mentioned Dr. Gumbel's wish to me and I immediately sent him a small quantity of North Atlantic mud from 2,350 fathoms, which had been preserved in spirit. The following translation of a letter, dated April 18th, 1870, with which Dr. Gumbel has favoured me, and which embodies the result of his researches hitherto, will, I am sure, be read with the greatest interest by geologists and biologists. I may mention that I long since found coccoliths in the nummulitic limestone of Egypt. T. H. Huxley
Many thanks for sending me the specimen of mud obtained by the deepest dredge. I have already subjected it to searching investigation, and have obtained results, which have the most important bearing upon my other work. Although my inquiries are, at present, only commenced, it will possibly interest you to receive some information respecting them. I call the new kind of investigations which I have begun to carry out, "Deep-sea investigations on the dry land " i.e., examinations of the different calcareous rocks, with reference to the share which the smallest organic forms, similar to those at present existing in the deep sea, have had in their formation. When limestone is soft and earthy, traces of the smallest marine animals can be detected by triturating it m water. In chalk, for instance, from Palestine, I have convinced myself, in the most unequivocal manners of the formation of the calcareous mass, for the greater part from your so-called coccoliths, besides Foraminifera, &c., which have long been known. Similar soft calcareous rocks are unfortunately rare in older formations. With these another process must be adopted. I started from the fact that in many of these calcareous rocks, the original calcareous portion of the organic beings is replaced by silica, and that hence in such rocks, by the separation of chert or flint, at least a part of the calcareous portion of the coccoliths and coccospheres might be replaced by silica. It was to be expected that the exterior form might suffer by this replacement, as, in fact, the chalk coccoliths have become materially different m their form from those of the existing deep-sea ooze.
I found, in fact, by treating such a siliceous limestone with very dilute acetic or hydrochloric acid, in the fine mud which is left, an organic residuum corresponding to the coccoliths of the present day. Even in the Trenton limestone, and in a yellow limestone of the Potsdam series, corresponding minute bodies were to be recognized, although sparingly, presenting themselves amongst an incredible multitude of other minute particles of organic origin. The microscope discloses, like the telescope, in the vault of heaven, a new world of the smallest organic beings, respecting which, however, I must say nothing at present, but confine myself to the coccoliths. These casts of coccoliths are found very sparingly. I explain this from the circumstance that the silica is chiefly the result of the decomposition of large masses of organic material, especially of the larger testacea. I obtained, however, important results by subjecting the deep-sea ooze, for which I am indebted to your kindness, to the action of the acids. These with violent development of carbonic acid, dissolve the minute bodies of the coccoliths, of the coccospheres, and perhaps also those of Bathybius (although of this I am not quite sure), and there remain only certain peculiarly formed but very much changed portions of the coccoliths as roundish discoidal flakes, the organic portion of the original coccoliths. In single isolated coccoliths this change of form is difficult to follow but this can easily be done in those which appear to be firmly bound up (enveloped?) with a mass of the granular flakes (Bathybius ?); and after the operation of the acid, can be again easily recognised in their exact position. Accompanying these coccoliths transformed by the action of acids, are countless little bodies extremely similar to those which can be obtained, in most cases, by dissolving siliceous limestone in acids.
This is the first commencement of researches which I propose following up, with, I hope, important results, since thin sections are of no good in studying these minute forms. I cannot close
these notes of the researches with which I am at [658] present engaged, without adding a further contribution, and hope not an unimportant one, to what is known respecting the nature of the deep-sea mud.
You speak of the chemical behaviour of these masses. The question whether these minute organisms represent animal or plants is still open. I have exposed the ooze to the action successively of a solution of iodine, of iodine and sulphuric acid, and of zinc chloride with potassium iodide, and have each time obtained in a remarkable manner a distinct blue colour, different shades from violet to green, in the substance of the coccoliths. There must therefore exist in the organism on the coccoliths, besides the calcareous skeleton, a kind of cellulose. Their organic nature is thus established beyond all doubt; but the conclusion might after all be drawn that we are dealing with plants, were it not that in the animal kingdom cellulose has been found in the Ascidians. But it is at all events interesting here on the boundary of organic life, to meet with cellulose. As a confirmatory test. I treated the substance with Millons' test which, as is well known, colours conchiolin red, but leaves the chitin of the Orthropoda on the other hand unchanged.
I obtained by this means no red colour in the flakes belonging to the coccoliths after the limestone had been dissolved by the excess of acid. A red colour showed itself, on the other hand
in many other particles, for instance, in the Polycistineæ whose siliceous coat was coloured red at the margins; and in irregular patches, which appeared to be derived from broken and crushed mussel-shells. 1 also noticed much deep brown and yellow colour. Especially by treatment with different chemical reagents, differentiated minute particles make their appearance which can scarcely be recognised by my microscope, and which, before the treatment with the chemical reagents, cannot be by any means detected. I expect that by this method an important extension of our knowledge of the most minute forms of organic life will be effected. I will only mention further that the red of the conchiolin shows itself of a bright red in the smallest particles which are found in such great numbers in the agglomerated flakes (Bathybius ), and which are smaller than the little elevations on the epidermal structures, which probably belong to Holothuridæ , and which frequently occur in the field of the microscope.
I should like to pursue further the chemical side of these investigations; but, unfortunately, the supply sent over to me is almost exhausted. If you consider these researches of sufficient importance to be worth continuing, and could obtain further material for me for this purpose, I should be greatly indebted to you. If you can make any use of this communication, it is at your service.
THE HUXLEY FILE