But it was only after Darwin that the cell-theory of Schwann was extended to the embryology of the animal kingdom generally, and that the knowledge of the development of an animal became a knowledge of the way in which the millions of cells of which its body is composed take their origin by fission from a smaller number of cells, and these at last from the single egg-cell.
The embryology of Myzostoma has been C A, Ventral view of Myzostoma.
Von Baer, however, has another place in the history of zoology, being the first and most striking figure in the introduction of embryology into the consideration of the relations of animals to one another.
Xix, ninth edition, PP 44 0 -44 1) has not met with acceptance, and until we have a fuller account of the embryology of some one form, preferably an Inarticulate, it is wiser to regard the group as a very isolated one.
The development of the compound microscope rendered possible the accurate study of their life-histories; and the publication in 1851 of the results of Wilhelm Hofmeister's researches on the comparative embryology of the higher Cryptogamia shed a flood of light on their relationships to each other and to the higher plants, and supplied the basis for the distinction of the great groups Thallophyta, Bryophyta, Pteridophyta and Phanerogamae, the last named including Gymnospermae and Angiospermae.
Development.-The embryology of the Nemertines offers some very remarkable peculiarities.
Gradually since the time of Hunter and Cuvier anatomical study has associated itself with the more superficial morphography until to-day no one considers a study of animal form of any value which does not include internal structure, histology and embryology in its scope.
The more important literature up to 1892 is given in the admirable treatise on Embryology by Professors Korschelt and Heider.
Heider, Handbook of the Comparative Embryology of Invertebrates (trans.
They are of interest, however, rather from the point of view of general embryology than from that of the special student of the Crustacea, and cannot be fully dealt with here.