He supposed that it consisted of free living protoplasm, covering a large part of the ocean bed. It is now known that the substance is of chemical, not of organic, origin.
More details about bathybius
Bathybius haeckeli was a substance that British biologist Thomas Henry Huxley discovered and initially believed to be a form of primordial matter, a source of all organic life. He later admitted his mistake when it proved to be just the product of a chemical process.
Huxley thought he had discovered a new organic substance and named it Bathybius haeckeli, in honor of the German philosopher Ernst Haeckel. Haeckel had theorized about Urschleim, "original slime", a protoplasm from which it was believed that all of life had originated. Huxley thought Bathybius could be that protoplasm, a missing link (in modern terms) between inorganic matter and organic life.
In 1868, Huxley studied an old sample of mud from the Atlantic seafloor taken in 1857. When he first examined it, he found only protozoan cells and placed the sample into a jar of alcohol to preserve it. Then he noticed that the sample contained an albuminous slime that appeared to be criss-crossed with veins.