m'clung: cytology and taxonomy. 207 



mation of the fertilization process, initiated by the union of 

 the spermatozoon and the ovum and rendered more intimate 

 by the fusion of the nuclei. There is not entire agreement 

 among observers regarding the exact time of the synapsis of 

 the chromosomes, but it is always described as occurring be- 

 tween the last spermatogonial division and the first sperma- 

 tocyte mitosis. In the grasshopper it is the final act of the 

 spermatogonial chromosomes, and precedes the changes of the 

 growth period. I am inclined to believe that it necessarily 

 does so. 



This act of synapsis is one that occurs only in the germ-cells, 

 and to me it has always seemed of the utmost importance. Let 

 us consider the conditions of the process a little more fully, and 

 see if something of value may not be gained in our search 

 for the cause of differentiation. The primordial germ-cells 

 have been more or less intimately a part of the body. Their 

 double sets of chromosomes have been functioning individually, 

 if not even antagonistically, and have built up cell-bodies of 

 considerable size. These early germ-cells are then gathered 

 together in a single place and are thereupon removed from so 

 intimate relations with the somatic cells. Under these condi- 

 tions, as we have noticed, they reproduce rapidly with constant 

 decrease in the amount of cytoplasm and end up with cells 

 almost entirely nuclear in proportion and strongly chromatic. 

 Here division ceases and the opposing paternal and maternal 

 chromosomes, their cytoplasmic environment practically gone, 

 unite together in synapsis. 



Conditions are evidently ripe for a change. The change be- 

 comes apparent in an altered behavior of the cell, which, no 

 longer expending its energies in reproduction, grows enor- 

 mously both in nucleus and cytosome. Reproduction has given 

 place to constructive metabolism. This is, however, such a met- 

 abolism as finds expression nowhere else in the life-cycle of or- 

 ganisms. Morphologically, at least, it accompanies a condition 

 in which the paternal and maternal chromosomes are reduced to 

 common units. Physiologically, I believe, it is a state wherein the 

 chromosomes, having passed through many generations of cells 

 in a cytoplasmic environment peculiar to the particular or- 

 ganism of which they are members, and having possibly ex- 

 hausted the metabolic resources of these conditions, unite their 

 common energies and construct a new cytoplasm. The extent 

 of this growth varies with the species, but in every case is con- 



