44 THE CELL 



sap ; these, being artificial products, must not be confused with the 

 normal structures. Hence cell-sap must contain various substances 

 in solution, amongst which albuminates are probably present; 

 Zacharias has grouped these together under the common name of 

 paralinin, a term which may well be dispensed with. 



The name AMPHIPYRENIN has been applied by Zacharias to the 

 substance of the membrane which separates the nuclear space 

 from the protoplasm, just as this latter is separated from the ex- 

 terior by the cell membrane. In many cases it is as difficult to 

 demonstrate the presence of this nuclear membrane, as to decide 

 the vexed question whether a large number of cells are enclosed 

 by membranes or no. It is most easily seen in the large germinal 

 vesicles of many eggs, such as those of Amphibians, where it is at 

 the same time somewhat dense in consistency. It is on this 

 account that it is so easy to extract the nucleus quite intact from 

 immature eggs with a needle. The nuclear membrane can be 

 ruptured, as a result of which its contents flow out, and may 

 be spread out in the liquid in which the examination is taking 

 place. But it seems to me to be equally certain that, in other 

 cases, a true nuclear membrane is absent, so that the nuclear sub- 

 stance and protoplasm come into direct contact. Thus Flemming 

 (II. 10), in the blood cells of Amphibians, and I myself, in the 

 sperm-mother-cells of Nematodes at a certain stage of their develop- 

 ment (Fig. 20 .B), have failed to discover a nuclear membrane. 



ALTMANN has endeavoured, by means of a special staining process with 

 cyanin, to demonstrate a granula structure in the nucleus as well as in the 

 protoplasm. By means of this process he has succeeded in intensely staining 

 the sap which fills up the interstices in the nuclear network, and in thus 

 showing up granula, whilst the nuclear network remains uncoloured, and is 

 designated intergra'iu'a substance. In this manner Altmann has obtained a, 

 so to speak, negative impression of the nuclear structure, as it becomes re- 

 vealed by staining the nuclear network with the usual nuclear staining 

 reagents. Since he considers that the granula form the most important part 

 of the nucleus, his opinion of the relative importance of the nuclear sub- 

 stances differs from the one which is generally accepted, and according to 

 which the nuclear sap is of less importance than the nuclein and par<mu- 

 clein. 



c. The Structure of the Nucleus. Examples of its 

 various Properties. The above-mentioned substances, of which 

 nuclein and paranuclein at any rate are never absent, occur in 

 very different forms in the nuclei of various plant and animal 

 cells ; this is especially true of nuclein, which may be present as 



