There is yet another line of thought which is weakening this early conception of the cell doctrine.  There is a growing conviction that the view of the organism, simply as the sum of the activities of the individual cells, is not a correct understanding of it.  According to this extreme position, a living thing can have no organization until it appears as the result of cell multiplication.  To take a concrete case, the egg of a starfish can not possess any organization corresponding to the starfish.  The egg is a single cell, and the starfish a community of cells.  The egg can, therefore, no more contain the organization of a starfish than a hunter in the backwoods can contain within himself the organization of a great metropolis.  The descendants of individuals like the hunter may unite to form a city, and the descendants of the egg cell may, by combining, give rise to the starfish.  But neither can the man contain within himself the organization of the city, nor the egg that of the starfish.  It is, perhaps, true that such an extreme position of the cell doctrine has not been held by any one, but thoughts very closely approximating to this view have been held by the leading advocates of the cell doctrine, and have beyond question been the inspiration of the development of that doctrine.

But certainly no such conception of the significance of cell structure would longer be held.  In spite of the fact that the egg is a single cell, it is impossible to avoid the belief that in some way it contains the starfish.  We need not, of course, think of it as containing the structure of a starfish, but we are forced to conclude that in some way its structure is such that it contains the starfish potentially.  The relation of its parts and the forces therein are such that, when placed under proper conditions, it develops into a starfish.  Another egg placed under identical conditions will develop into a sea urchin, and another into an oyster.  If these three eggs have the power of developing into three different animals under identical conditions, it is evident that they must have corresponding differences in spite of the fact that each is a single cell.  Each must in some way contain its corresponding adult.  In other words, the organization must be within the cells, and hence not simply produced by the associations of cells.

Over this subject there has been a deal of puzzling and not a little experimentation.  The presence of some sort of organization in the egg is clear—­but what is meant by this statement is not quite so clear.  Is this adult organization in the whole egg or only in its nucleus, and especially in the chromosomes which, as we have seen, contain the hereditary traits?  When the egg begins to divide does each of the first two cells still contain potentially the organization of the whole adult, or only one half of it?  Is the development of the egg simply the unfolding of some structure already present; or is the structure