iSge. ZOOLOGY SINCE DARWIN. 195 



However premature under the then existing conditions of zoology 

 these pedigrees may have been, there is due to them the immortal 

 credit of having given the first impetus to the grand revolution in 

 animal morphology of the last decades. Modern comparative 

 anatomy dates from this period, in which C. Gegenbaur w^orked side 

 by side with Haeckel. It has since then so completely become the 

 chief part of scientific zoology, that our present text-books are given 

 up almost exclusively to comparative morphology. The biogenetic 

 ]-»rinciple formulated by Haeckel — that ontogeny (evolutionary history 

 of the individual) is a short recapitulation of the phylogeny (history 

 of the stock) — soon overmastered all branches of zoology, pervading 

 comparative anatomy, evolution, and palaeontology. Since the forms 

 passed through by the ancesters of any animal are reflected, more o 

 less recognisably, in the temporary varieties of forms during the indi- 

 vidual's own development, evolution became the chief doctrine of 

 post-Darwinian time. Its chief result at first was an enormous 

 increase of zoological publications, about 2,900 on an average for one 

 year being published in the period 1 845-1 860, and about 5,400 per year 

 between 1861-1880.^ Hand in hand with this increase in literary 

 productions proceeded the improvement in the technique of research. 

 Innumerable methods of staining permitted the growth of the cell to 

 be more exactly studied, the cell-plasma and the nucleus and its 

 elements to be separated according to their different staining capacities. 



The tissues of the body, ^.o-., muscles, nerves, and ligaments, nay, 

 even the different stages of efficacy of the cells of one and the same 

 organ, e.^., the glands, could be separated in microscopic appearance 

 by such new methods of coloration and impregnation. The old 

 "pick and bruise" technique was supplanted by the microtome, 

 whose pricelessness lies in its enabling us to dissect an animal in an 

 uninterrupted series of extremel}' fine sections. Since by such means 

 we can reconstruct the tissue of an object down to its elemental parts, 

 we are now in a position to examine the inner structure of animals, 

 whose small size had denied all information to the anatomical knife, 

 or whose opaqueness had defied the bruise-meihod. And, moreover, 

 let us remember the great advance in the serviceableness of the 

 microscope by the construction of the new apochromatic lenses. 



All this came as a great help to morphology, and in no earlier 

 period of zoology had so many comprehensive and profound zootomical 

 and embryological monographs been issued. The aim of almost all 

 of these was the proving of the genealogical tree. While, however, 

 the work of comparative anatomy was chiefly to elucidate the relation- 

 ships of present day forms, evolution strove, in the incompleteness of 

 palaeontological results, to elucidate the older stages of animal history 

 by a comparison of ontogenetic forms. One result of this striving is 



1 The authorities for these figures are the " Eibliotheca zoologica," by J. V. 

 Carus and W. Engelmann, Leipzig, 1S61, and the " Bibliotheca zoologica," 11., by 

 O. Taschenberg, Leipzig, 1SS7-1896. 



P 2 



