VIII] OR CELL-AGGREGATES 401 



A section across the cylinder, then, will tend to shew us precisely 

 the same arrangements as we have already so fully studied in 

 connection with the typical division of a circular cell into quadrants, 

 and of these quadrants into triangular and quadrangular portions, 

 and so on. 



But there are other possibilities to be considered, in regard to 

 the mode of division of the elongating quasi-cyhndrical portion, as 

 it gradually develops out of the growing and bulging quadrantal 

 cell; for the manner in which this latter cell divides will simply 

 depend upon the form it has assumed before each successive act 

 of division takes place, that is to say upon the ratio between its 

 rate of growth and the frequency of its successive divisions. For, 

 as we have already seen, if the growing cell attain a markedly 

 oblong or cylindrical form before division ensues, then the partition 

 will arise transversely to the long axis ; if it be but a little more 

 than a hemisphere, it will divide by an obhque partition ; and if 

 it be less than a hemisphere (as it may come to be after successive 

 transverse divisions) it will divide by a vertical partition, that is 

 to say by one coinciding with its axis of growth. An immense 

 number of permutations and combinations may arise in this way, 

 and we must confine our illustrations to a small number of cases. 

 The important thing is not so much to trace out the various 

 conformations which may arise, but to grasp the fundamental 

 principle : which is, that the forces which dominate the form of 

 each cell regulate the manner of its subdivision, that is to say 

 the form of the new cells into which it subdivides; or in other 

 words, the form of the growing organism regulates the form and 

 number of the cells which eventually constitute it. The complex 

 cell-network is not the cause but the result of the general configura- 

 tion, which latter has its essential cause in whatsoever physical 

 and chemical processes have led to a varying velocity of growth 

 in one direction as compared with another. 



In the annexed figure of an embryo of Sphagnum we see a 

 mode of development almost precisely corresponding to the 

 hypothetical case which we have just described, — the case, that 

 is to say, where one of the four original quadrants of the mother- 

 cell is the chief agent in future growth and development. We 

 see at the base of our first figure {a), the three stationary, or 

 T f- 26 



