STUDIES ON CHROMOSOMES. 237 



somes conspicuously laid down in advance as nucleolar-like 

 bodies, after the manner recorded as so characteristic in insects. 

 Spiremes and synizetic stages may be found occasionally which 

 show one or more chromatin condensations which might be 

 interpreted as nucleoli but they rarely show anything in size or 

 shape which could lead one to identify them with the curved 

 elements of the spermatogonia or of the larger special element 

 found later in the spermatocytes. 



Figs. 125 to 132, in which all details have been depicted as 

 accurately as possible, show representative views of an inter- 

 esting condition which exists just prior to the formation of the 

 chromosomes in the primary spermatocytes. The spireme of 

 such a stage as that shown in Fig. 124 seems gradually (Fig. 

 125) to break up into a series of characteristic smaller and larger 

 chain-like groups. In some of these it is difficult to decide 

 whether each formation consists of a series of transparent, bead- 

 like bodies encased in a thin shell of deeply staining material, 

 or whether it arises through the twisting of two filaments one 

 about the other. The latter is certainly the condition in some 

 cases, particularly of the smaller elements where the free ends 

 of the threads are distinctly visible, as for instance in Fig. 130, 

 and I am inclined to think that it also prevails in the other 

 instances. The formations thus established condense gradually 

 into bodies of smaller size, certain ones of which, at least, take 

 on the appearance that is so characteristic of some types of 

 tetrads (Fig. 132). Even in metaphase, when the chromosomes 

 of the primary spermatocytes are well established, a tetrad-like 

 condition of individual chromosomes may occasionally be de- 

 tected in strongly decolorized preparations. In some instances, 

 indeed, one member of such four-groups apparently becomes 

 displaced and divides as a smaller, independent member, thus 

 confusing the chromosome count. Occasionally this seems to 

 occur in more than one member of a given set of chromosomes 

 so that two or more of such quarter-sized individuals may appear 

 at the formation of the equatorial plate stage. 



As noted in my earlier paper ('096) there are frequent nuclear 

 divisions without a corresponding division of the surrounding 

 cytoplasmic mass. Commonly from two to four large primary 



