PROF. STRASBURGEr's OBSERVATIONS ON PROTOPLASM. 129 



applied, and forms, with the remaining endoplasm, a smaller 

 protoplasmic mass lying free within the cellulose envelope. 

 Within a few minutes a fresh cellulose membrane could be 

 detected on the surface of this small mass of protoplasm. On 

 one occasion this process was repeated three times. Hence 

 it appears that the secretion of a cellulose envelope is closely, 

 and even inseparably connected with the presence of an 

 ectoplasmic layer (Fig. 6). 



2. The endoplasm. 



Heitzmann and Frommann have recently pointed out that 

 the substance which forms the basis of the endoplasm often 

 presents a reticulated structure, and Professor Strasburger 

 found the same to be the case in the ovules of Coniferse and 

 Gnetacese, and laid stress upon the distinction to be drawn 

 between vacuoles and chambers in protoplasm. Vacuoles are 

 drops of a watery fluid surrounded by protoplasm, whereas 

 chambers are formed when the cell-sap is traversed by 

 numerous anastomosing plates of protoplasm. Such a series 

 of chambers may be seen in the anterior clear space of the 

 zoogonidia of Vaucheria (Fig. 2). 



In many young, and in most mature vegetable cells the 

 endoplasm forms a thinner or thicker layer on the inner side 

 of the ectoplasm. If, under these circumstances, the endo- 

 plasm attains a considerable thickness, a distinction can be 

 drawn between its external and internal portions, the former 

 being apparently of greater density than the latter. This 

 is indicated by a difference in the granules imbedded in the 

 one and in the other, and also by the fact that the inner 

 layers are often found to be in motion, whilst the outer are 

 at rest. 



Under the influence of the dividing nucleus the hyaline 

 substance forming the basis of the endoplasm of animal cells 

 assunies, during the process of division, a distinctly radial 

 arrangement, the hyaline rays extending for some distance 

 from the two poles of the nucleus. From this it appears that 

 the granules of the endoplasm are repelled from the poles 

 of the nucleus. 



During the formation of chlorophyll- grains the endoplasm 

 undergoes a diflierentiation as well marked as that above 

 described occurring during the process of cell -division. That 

 these structures really belong to the endoplasm is shown by 

 the fact that, in many of the lower algse, the whole of the 

 endoplasm is coloured green, the ectoplasm alone remaining 

 colourless, and yet they are of greater density than the en- 

 doplasm in which they are placed, and they do not present 



