18 JOURNAL OF THE [January, 



protoplasm figures, not quite accurately, perhaps, as the one 

 material thing which is the same yesterday, to-day, and forever. 



I have already said, however, that the ideal protoplasm of the 

 philosophers and the actual protoplasm known to the biologists are 

 two very different matters. The former, you will remember, is a 

 colorless, homogeneous, structureless colloid, like glycerin ; but 

 the veritable thing which we are able to get under the microscope 

 is always much less simple in appearance and is generally com- 

 plicated with other substances. The endochrome of the diatom, . 

 for example, is usually spoken of as if it were wholly protoplasm, 

 when in fact it is made up of soft parts and harder parts, trans- 

 parent spots and nearly opaque spots, liquids, semi-liquids, and 

 solids, together with the green chlorophyll and a brown coloring 

 matter, and, in addition to the vacuoles of which I spoke some 

 time ago, veritable oil drops, which are supposed to correspond 

 with the starch-granules of the higher plants. Under the micro- 

 scope the endochrome therefore looks like what it really is, — a 

 mixture of numerous substances of various colors and consisten- 

 cies, with, however, a tendency to greater and greater density 

 towards a certain central spot which has always been an object 

 of great interest to investigators. This area of condensation is 

 known as the nucleus. Formerly undue mystery was attached to 

 it, as the supposed shrine of the vital spirit. Here, it was fancied, 

 life had been traced to its ultimate hiding-place. It was believed 

 that there could not be a living unit without its nucleus, and, as 

 the anatomical unit was taken to be a closed vesicle, called a cell, 

 all living creatures were, in the last analysis, reduced to a single 

 ■cell with its nucleus, or to an aggregate of such cells. But by 

 and by it was found that the enclosing vesicle was no essential 

 part of the ultimate unit, — that in fact it was a product of the 

 enclosed protoplasm and, being later in time, must be subordinate 

 in importance. Then the cell-theory was modified into the proto- 

 plasm-theory, and the unit became a lump of protoplasm with its 

 nucleus. But, just as the increasing power of the telescope has 

 compelled a change in our ideas of the nebulae, by making wha 

 were formerly mere condensations of light resolve themselves into 

 numberless clusters of universes and worlds, with their own cen- 

 tres of force and activity, so the improvement of the microscope 

 has forced upon biologists a recasting of their theories of the 



