The popular image of Thomas Henry Huxley (above) is as "Darwin's Bulldog", after his strong support for evolution in a debate with Bishop Wilberforce of Oxford. He was, of course, a distinguished scientist and Natural Historian, all the more surprising as he had little formal school education. However, Huxley was dedicated to reading and to "improving himself" and was eventually accepted to study Medicine, although he didn't complete a degree. This medical training was sufficient for him to be appointed assistant ship's surgeon on H.M.S. Rattlesnake and this gave him the opportunity to study Natural History while at sea, an interest he maintained. Like others at the beginning of the 19th Century, he used microscopes to reveal otherwise unknown organisms and he discovered Bathybius haeckelii. This was subsequently shown to be an artefact, which caused some to deride Huxley. Not me. I admire his courage in admitting his error and in openly facing the consequences.
This is the story.
Huxley writes :
In the year 1857, H.M.S. "Cyclops", under the command of Captain Dayman, was despatched by the Admiralty to ascertain the depth of the sea and the nature of the bottom in that part of the North Atlantic in which it was proposed to lay the telegraph cable, and which is now commonly known as the "Telegraph plateau."
Later in the article, Huxley describes possible organisms that he found  and:
..[the] structure to be observed in the gelatinous matter of the Atlantic mud, and in the coccoliths and coccospheres [found there]. I have hitherto said nothing about their meaning, as in an inquiry so difficult and fraught with interest as this, it seems to me in the highest degree important to keep the questions of fact and the questions of interpretation well apart.
Note how Huxley stresses the need to separate fact from interpretation. However, it was in the interpretation of what he observed that an error crept in. Despite his caution, he goes on :
I conceive that the granule-heaps and the transparent gelatinous matter in which they are imbedded represent masses of protoplasm. Take away the cysts which characterise the Radiolaria, and a dead Sphærozoum would very nearly resemble one of the masses of this deep-sea "Urschleim," which must, I think, be regarded as a new form of those simple animated beings which have recently been so well described by Haeckel in his "Monographie der Moneren." I propose to confer upon this new "Moner" the generic name of Bathybius, and to call it after the eminent Professor of Zoology in the University of Jena, B. Haeckelii.
After this, Bathybius (see below) was discovered in other samples of marine mud and it was concluded that it had a world-wide distribution. Furthermore, it gained the status of being a link between non-living and living matter [2,3]. Darwin's theory of evolution had inevitably raised questions about the earliest forms of life and Bathybius fitted that niche. Huxley's initial observations were made two years before Darwin published On the Origin of Species, yet the naming of the organism came nine years after the publication of that hugely important work.
Other Natural Historians were sceptical of the validity of Bathybius. In 1873, Wyville Thomson published The Depths of the Sea describing dredging cruises made by H.M.S. Porcupine and H.M.S. Lightning in 1868-70:
I feel by no means satisfied that Bathybius is the permanent form of any distinct living being. It has seemed to me that different samples have been different in appearance and consistence; and although there is nothing at all improbable in the abundance of a very simple shell-less "moner" at the bottom of the sea, I think it is not impossible that a great deal of the "bathybius", that is to say the diffused formless protoplasm which we find at great depths, may be a kind of mycelium – a formless condition connected either with the growth and multiplication or with the decay – of many different things.
G.C. Wallich had suggested that some of the components of Bathybius were settled fragments from higher in the water column  and the living nature of the organism was further criticised in a letter that Wyville Thomson wrote to Huxley in 1875 after another dredging cruise . These two extracts are from Huxley's note on this letter in Nature :
Professor Wyville Thomson further informs me that the best efforts of the "Challenger's" staff have failed to discover Bathybius in a fresh state, and that it is seriously suspected that the thing to which I gave that name is little more than sulphate of lime, precipitated in a flocculent state from the sea-water by the strong alcohol in which the specimens of deep-sea soundings which I examined were preserved..
..Professor Thomson speaks very guardedly, and does not consider the fate of Bathybius to be as yet absolutely decided. But since I am mainly responsible for the mistake, if it be one, of introducing this singular substance into the list of living things, I think I shall err on the right side in attaching even greater weight than he does to the view which he suggests.
With that, Huxley admitted his earlier mistake but, after his prominent role in championing the views of Darwin, he continued to receive disapprobation from those who opposed them. Rehbock  quotes one of these:
Huxley's folly was utilized, with similar intent, by William Mallock, the writer and theologian, in 1890. Mallock's article solicited a delightfully typical response from the "bishop-slayer," who was by then feeling some exasperation. This reply is the last recorded event in the history of Bathybius in which its creator took part:
Bathybius is far too convenient a stick to beat this dog with to be ever given up, however many lies may be needed to make the weapon effectual.
I told the whole story in my reply to the Duke of Argyll, but of course the pack give tongue just as loudly as ever. Clerically-minded people cannot be accurate, even the liberals.
This was 15 years after Huxley's note in Nature accepting the likelihood that Bathybius was not an organism and his error is even brought up by some creationists today to try and discredit his views on evolution.
What is clear in the story of Bathybius is the ease by which established scientists can become carried away by current theories, despite a natural caution against speculation. It is as true today as it was in the Nineteenth Century, especially among those who ponder the origins of life, as did Huxley in 1862 :
..the causes of the phenomena of organic nature resolves itself into two problems – the first being the question of the origination of living or organic beings; and the second being the totally distinct problem of the modification and perpetuation of organic beings when they have already come into existence. The first question Mr. Darwin does not touch; he does not deal with it at all; but he says – given the origin of organic matter – supposing its creation to have already taken place, my object is to show in consequence of what laws and what demonstrable properties of organic matter, and of its environments, such states of organic nature as those with which we are acquainted must have come about. This, you will observe, is a perfectly legitimate proposition; every person has a right to define the limits of the inquiry which he sets before himself; and yet it is a most singular thing that in all the multifarious, and not infrequently, ignorant attacks which have been made upon the "Origin of Species," there is nothing which has been more speciously criticised than this particular limitation.
It is thus easy to see Huxley's mind set when he recalled the samples from 1857. Yet both Huxley and Wyville Thomson were on to something when they stressed the importance of organic matter on the ocean floor, as we were to discover years later.
 T.H.Huxley (1868) On some organisms living at great depths in the North Atlantic Ocean. Quarterly Journal of Microscopical Science 8:203-212.
 Nicolaas A. Rupke (1976) Bathybius Haeckelii and the psychology of scientific discovery. Studies in History and Philosophy of Science 7:53-62
 Philip F. Rehbock (1975) Huxley, Haeckel, and the Oceanographers: The Case of Bathybius haeckelii. Isis 66:504-533.
 C. Wyville Thomson (1873) The Depths of the Sea. London, Macmillan and Co.
 T.H.Huxley (1875) Notes from the "Challenger". Nature 12:315-316.
 T.H.Huxley (1862) On our knowledge of the causes of the phenomena of organic nature. London, Robert Hardwicke.