. Natural science: a monthly review of scientific progress . raptidae, in the same way as in 1895 ^ derived different groups•of Monogvaptiis, each by way of its corresponding Dimovphogyaptus,from Diplograptns and Climacogvaptus respectively (18). Fig. 9, taken from Ruedeman (17) shows that colonies ofDiplograptiis were united by their virgulae into brush-like or almoststar-shaped colonies of a higher order, within which there was adivision of labour. Beside the Diplograpti in the ordinary sense, 192 NATURAL SCIENCE. September, 1896. easily recognised on the figure, we see a great number of org
. Natural science: a monthly review of scientific progress . raptidae, in the same way as in 1895 ^ derived different groups•of Monogvaptiis, each by way of its corresponding Dimovphogyaptus,from Diplograptns and Climacogvaptus respectively (18). Fig. 9, taken from Ruedeman (17) shows that colonies ofDiplograptiis were united by their virgulae into brush-like or almoststar-shaped colonies of a higher order, within which there was adivision of labour. Beside the Diplograpti in the ordinary sense, 192 NATURAL SCIENCE. September, 1896. easily recognised on the figure, we see a great number of organs ofdifferent nature grouped round the central point of union ; to theseRuedeman gives the general name of central organs. But his work,which is described as preliminary, does not give us enough infor-mation about these organs. For the present then I would merelyremark that a in Ruedemans Fig. 4 can scarcely be regarded as agonangium, which means an individual or organ for sexual propa-gation ; but that it ought rather to be considered as an individual. Fig. 9.—Colonies of Diplograptus (after Ruedemann). for sexless propagation, a budding individual. It is of interest to getan explanation of the significance of the hollow virgula, so difficultto understand before. Because of this discovery, we cannot butconclude that all graptoloids were, at least temporarily, connectedin this way so as to form parts of colonies of a higher order. Thisdiscovery may also give us valuable information as to the mode oflife of the Graptoloidea. Upsala. Carl Wiman. {To he continued.) 193 VI. ZoolooT since Darwin. WE younger men, whose scientific education begins under thejurisdiction of Darwin, can reahse only with difficulty the ex-citement which his work on the origin of species- caused almostforty years ago in the realm of the natural sciences. It fell like athunderbolt during a period of calm descriptive work, a period whichhad accustomed itself to regard the natural-philosophy ideas
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