M'cLUNG : SPERMATOCYTE DIVISIONS OF THE ACRIDID.E. 87 



gretted that, after having so far appreciated the character of the 

 structure, he should confuse the nomenclature by applying the 

 (pialifying term "small" to it. The argument (26, p. 251) he so 

 justly uses against the word "mitosome" applies with equal force in 

 the present instance, and condemns the expression "small chromo- 

 some" as a misnomer, because, in most insects, this chromosome ex- 

 ceeds all the others in size. Accordingly, the preliminary term will 

 be continued until a more fitting one is found. 



IV. — COMPARISONS AND CONCLUSIONS. 



With due regard to the importance of theoretical and comparative 

 work, I hope to avoid what is certainly an error : the erection of a 

 large superstructure of theory upon a small foundation of fact. Only 

 the comparative study of numerous forms can serve as the basis for 

 any far-reaching theories, and this, I believe, is yet to be accom- 

 plished. Since, however, the ground must first be cleared by weed- 

 ing out the errors that unavoidably sjDring up in i3reliminary work of 

 this kind, I venture to suggest instances wherein such mistakes ap- 

 pear to have been made by other investigators. In order to facilitate 

 such a discussion, the generally accepted facts of the subject will be 

 outlined in the beginning, 



In the process of germ-cell formation in the male organism, there 

 are three generally recognized stages. The first of these includes the 

 changes by means of which the primordial germ cell, by rapid and 

 repeated divisions, gives rise to a large number of cells, commonly 

 called spermatogonia. These changes are included under what is 

 usually termed the "division period." At its conclusion there are to 

 be found in the sexual organ considerable numbers of cells which do 

 not enter into division, but gradually increase in size during the early 

 prophase of a long-delayed mitosis. These cells are then said to be 

 passing through the "growth i^eriod." This prolonged existence in 

 tlie prophase is an evident preijaration for the unusual and character- 

 istic divisions which follow. The essential features of these are the 

 lialving of the usual number of chromosomes, the production of others 

 that are quadripartite in character, and the sej)aration of these by two 

 rapid divisions without an intervening resting stage. These fall 

 within the •'maturation period," so called. In the process of sperma- 

 togenesis, there follows a series of transformations, as a result of which 

 tlie cells are converted into the highly specialized elements known as 

 spermatozoa. 



With these facts accepted, there remain to be determined the 

 means by which the number of chromosomes is reduced, and the 

 methods by which the tetrads are separated without entering into a 



