252 The Development of the Neuroglia 



largest individual surface of the protoplasm connected with the nucleus. 

 The precipitation is at first much less extensive upon the more attenuated 

 collateral filaments connecting the radial axes, and fortunatel}^ so, for 

 were these all covered, the sections, necessarily thick to show the entire 

 course of the axes, would be clogged. The few of the connecting threads 

 that are shown are usually shown for only a short extent. 



By comparing Fig. 7 with Fig. 11 it appears, by the silver method, 

 that the radial axes increase in size with the growth of the animal from 

 15 to 70 millimeters. Staining methods applied to these stages do not 

 show so marked an increase in size. Also in Fig. 7 (15 millimeters) 

 the precipitation of the reduced salt is evidently not so complete as in 

 the other figures. Both of these variations may indicate a development 

 of the selective property, for in pigs of less than 10 millimeters I have 

 been unable to obtain a differential precipitation at all. 



The bifurcations of the axial filaments, the formation of which has 

 been already described, are very evident by the silver method but are 

 barely suggested in the stained preparations. This is not wholly due to 

 the difference in the thickness of the two sections represented in each 

 drawing (80/a compared with ofx), but is also due to the fact that the 

 whole of the syncytium is shown in the' thinner section and but a part 

 of it in the silver preparation. 



The greater complexity in the arrangement of the syncytial filaments 

 along the boundary line between the nucleated and the mantle layer {h, 

 see figures) is shown by both methods but more clearly by the silver. 

 Its formation begins early, as shown in Figs. 3 and 4, but its increased 

 complexity in the later stages (Figs. 7 to 10) more fully suggests 

 that it may, for a time, prevent the nuclei from migrating into the 

 mantle layer. At 7 centimeters (Fig. 11), axones are more abundant 

 and the boundary line begins to be broken up, and the nuclei begin to 

 invade the mantle layer rapidly, till at 8 and 9 centimeters, nuclei become 

 almost as abundant in the mantle as in the middle layer. 



At the point of bifurcation, where the filaments come together, there 

 is a greater amount of the plastic substance than in the simple diameter 

 of a filament. Both because of this and also due to the angles formed 

 by the junction, there is usually a greater deposit of the silver salt at 

 these points than elsewhere and the precipitation usually tends to run 

 further out on the collateral filaments. There seems to be a progressive 

 increase of this phenomenon from 15 millimeters upward. In pigs of 

 55 millimeters the points of bifurcation {h. Fig. 10), if isolated, would, 

 to say the least, strongly resemble the " astroblasts " and " astrocytes " 

 described by various authors (Eeinke, Kolliker, Lenhossek, etc.). And 



