continuous development.” However, these are words that might have been written by Schleiden or Unger or Bronn before Darwin’s time. Yet there is something in the work that would have been a jet of ice-cold water to the Agassizs and Giebels. This brilliant new “Extraordinary Professor of Zoology and Director of the Zoological Museum at Jena University,” as it says on the title-page, accepts Darwin in a certain unambiguous passage late in the text. It is necessary to bring to light once more this passage, buried in a work that is not easily accessible, an expensive technical work separated from us by four decades now. It is worth doing so, not only on account of the courage it displayed at the time, but also as a document relating to the great controversy of the nineteenth century. It is found on pages 231 and 232, partly in the text, but for the most part in a note. Immediately after giving the table of classification Haeckel goes on to say: “I cannot leave this general account of the relationship of the various families of the radiolaria without drawing special attention to the numerous transitional forms that most intimately connect the different groups and make it difficult to separate them in classification, to some extent.” It is interesting to note that in spite of our very defective knowledge of the radiolaria it is nevertheless possible to arrange “a fairly continuous chain of related forms.” He would like to draw particular attention to this, because “the great theories that Charles Darwin has lately put forward, in his _Origin of Species in the Plant and Animal World by Natural Selection, or The Preservation of the Improved Races in the Struggle for Life_, and which have opened out a new epoch for systematic biology, have given such importance to the question of the affinities of organisms and to proofs of continuous concatenation that even the smallest contribution towards the further solution of these problems must be welcome.” He then endeavours in the text, without any more theoretical observations, practically to construct a “genealogical tree of the radiolaria,” the first of a large number of such trees in the future. He takes as the primitive radiolarian a simple trellis-worked globule with centrifugal radiating needles, embodied in the _Heliosphæra_. “At the same time,” he says, characteristically, “this does not imply in the least that all the radiolaria must have descended from this primitive form; I merely show that, as a matter of fact, all these very varied forms may be derived from such a common fundamental type.” In other words, once more, it is _conceivable_—a golden word even long afterwards. The first “genealogical tree,” a “table of the related families, sub-families, and genera of the radiolaria,” arranged in order from the higher forms down, and connected with lines and brackets, comes next. The text deals thoroughly with the possibility of descent. This closes the first and general part of the monograph.