CYTOPLASM OF ANIMAL AND PLANT CELLS. 5 



foreign bodies into protoplasm usually lead to remarkably little 

 reaction. 



THE EFFECT OF CHEMICAL TREATMENT AND OPERATIONS ON 

 THE PERMEABILITY OF CELLS. 



Early in this investigation a general relation between per- 

 meability and the degree of concentration of protoplasmic gels 

 was noted. Several methods were devised for grading the con- 

 centration of the surface and interior portions of the cytoplasm 

 of various cells. The desired concentration gradient can be 

 produced in the 'eggs of Asterias, Chcztopterus, Cumin gia,- and 

 Nereis either by treating with very dilute acids, alkalies and 

 saponin dissolved in sea water or puncturing or cutting with 

 extremely fine Jena glass needles. It was proved that such 

 operative treatment does not kill any portion of the egg. 



If the egg of Asterias be punctured, the acid dyes used penetrate 

 the swollen area for varying depths, but never enter the normal 

 unswollen cytoplasm. Under the conditions of my experiments 

 only the swollen surface was penetrated and stained. It cannot 

 be overemphasized that the concentration gradient experiment 

 has proved an adequate test of the correctness of the membrane 

 conception, at least for the eggs of Asterias, Cumingia, Chcetop- 

 terus and Nereis. Dyes w r ere selected which do not penetrate 

 the normal egg. These dyes penetrate the swollen cytoplasm 

 produced by the operation or chemical treatment, to varying 

 depths, but never enter the unswollen cytoplasm. Some of the 

 acid dyes do not penetrate the surface of the swollen area of a 

 punctured egg, while others are stopped only by the unchanged 

 cytoplasm. These results are exactly the converse of what 

 would necessarily follow if the plasmatic membrane conception 

 were really true. Moreover, it was noted that trypan red and 

 erythrosin stain the surface of a .normal Chcetopterus egg, but 

 even a great increase in concentration of the dyes does not pro- 

 duce more than a surface staining. Here the surface is actually 

 more permeable to these dyes than the interior of the egg. Again, 

 the nucleus of the eggs of Asterias, Cumingia, Chcetopterus, and 

 Nereis remain unstained when the eggs are placed in the best 

 vital stains in use at the present time. Under this set of condi- 



