The first phenomenon which can be observed after impregnation is the conglomeration of the yolk spheres into cylindrical columns, which finally assume a radiating form diverging from the centre of the egg. In the centre of the radiate figure is a protoplasmic mass, probably containing a nucleus, which sends out protoplasmic filaments through the columns (fig. 53 A). After a certain period of repose the figure becomes divided into two rosette-like masses, which remain united for some time by a protoplasmic thread: this thread is finally ruptured (fig. 53 B). The whole egg does not in this process divide into two segments, but merely the radiate figure, which is enclosed in a finely granular material. The two rosettes next become simultaneously divided, giving rise to four rosettes (fig. 53 C): and the whole process is repeated with the same rhythm as in a regular segmentation till there are formed thirty-two rosettes in all (fig. 54 A). The rosettes by this time have become simple columns, which by mutual pressure arrange themselves radiately around the centre of the egg, which however they do not quite reach. [FIG. 54. SURFACE VIEW AND OPTICAL SECTION OF A LATE STAGE IN THE SEGMENTATION OF PHILODROMUS LIMBATUS (Koch). (After Hub. Ludwig.) _bl._ blastoderm; _yk._ yolk spheres.] When only two rosettes are present the protoplasm with its nucleus occupies a central position in each rosette, but gradually, in the course of the subsequent subdivisions, it travels towards the periphery, and finally occupies, when the stage with thirty-two rosettes is reached, a peripheral position. The peripheral protoplasm next becomes separated off as a nucleated layer (fig. 54 B). It forms the proper blastoderm, and in it the nuclei rapidly multiply and finally around each an hexagonal or polygonal area of protoplasm is marked off; and a blastoderm, formed of a single layer of flattened cells, is thus constituted. The columns within the blastoderm now form (fig. 54 B) more or less distinct masses, which are stated by Ludwig to be without protoplasm. From observations of my own I am inclined to differ from Ludwig as to the nature of the parts within the blastoderm. My observations have been made on _Agelena labyrinthica_ and commence at the close of the segmentation. At this time I find a superficial layer of flattened cells, and within these a number of large polyhedral yolk cells. In many, and I believe all, of the yolk cells there is a nucleus surrounded by protoplasm. It is generally placed at one side and not in the centre of a yolk cell, and the nuclei are so often double that I have no doubt they are rapidly undergoing division. It appears to me probable that, at the time when the superficial layer of protoplasm is segmented off from the yolk below, the nuclei undergo division, and that a nucleus with surrounding protoplasm is left with each yolk column. For further details _vide_ Chapter on Arachnida.