104 The American Naturalist. [February, 



The first and simplest reproduction is a simple, almost 

 mechanical fission or breaking apart of a naked mass of pro- 

 toplasm, which is nevertheless an organized being, as seen in the 

 fission of the swarm spores of Myxomycetes, in other Protozoa 

 and Protophyta. The body of the organism, after a lengthened 

 period of growth, readies a size where the proportion of the 

 surface to the bulk is not sufficient to provide suitable nourish- 

 ment for its continued growth. Thus a division or multiplica- 

 tion of the body is necessitated to provide greater surface for 

 absorption. 



In a thorough consideration of these facts, we come to see 

 how intimately growth and reproduction are associated, 

 growth being nothing more than a protoplasmic and usually 

 cellular reproduction. We are very apt to think of cell divi- 

 sion as a necessary accompaniment of growth. But this is not 

 so. Growth is independent of cell multiplication. Cell divi- 

 sion need not take place during growth, but may appear only 

 after its conclusion. In Stypocaulon, an alga belonging to the 

 Phseosporea? the lateral branches of the frond, as pointed out 

 by Geyler, attain their full size before the formation of cells 

 begins. Cells are then formed from the base upward, until finally 

 the branch, which was a single cell, becomes a normal multi- 

 cellular organ. One of the most remarkable cases illustrating 

 this point is found in Caulerpa, a seaweed, the whole vegetative 

 body of which remains throughout life an enormous single 

 cell. (Fig. 1, a portion of frond, natural size). In the cavity 

 of this thick walled vescicle, however, numerous cross bars of 

 cellulose are found to give greater strength. In the common 

 green felt (Vaucheria) even these cross bars are wanting. Cell 

 division, however, usually accompanies growth and as shown 

 above is in most cases a necessity to provide sufficient nutri- 



CELL REPRODUCTION. 



The phenomena of cell reproduction or division are so inti- 

 mately connected with the consideration of all phenomena ot 

 reproduction and fecundation that it is necessary for us to 

 briefly consider this subject as a preparatory step. The changes 

 which take place in the cell nucleus seem to be of paramount 



