534 CLARENCE E. McCLUNG 



strongly suggested. Because of the constancy of chromosome 

 organization, indicated among other ways by the constancy of 

 fiber attachment, we would be justified in saying that the V's 

 of the spermatogonium unite in synapsis to form the first sper- 

 matocyte multiple and that this should appear with two non- 

 terminal fiber attachments. Such a condition is reahzed in the 

 structure of the hexad in the first spermatocyte mataphase. 



The conditions of the first spermatocyte complex in meta- 

 phase are readily determined, particuiaiiy if sections of sufficient 

 thickness are used, and in smears are almost diagrammatic. 

 Here there are clearly eleven chromosomes present, among which 

 is a very large and distinctly different shaped one (figs. 55, 56, 

 57, pi. 7), This is characteristically in the form of a rod with 

 the two ends of shghtly different length bent sharply back in 

 the same plane. One or both of the ends may exceed, or fail 

 to reach, the common angle, producing some variety in form. 

 Greater or less extension, preparatory to division, may result in 

 considerable variation in length, but commensurate and opposite 

 changes in diameter show that the volume remains very constant. 

 Indications of internal composition are afforded by the contour 

 of the element, although, as will be shown later, they are not 

 entirely trustworthy. At each of the bends, where the fibers 

 attach, there is a constriction, and nearer the shorter bent end, 

 at about its length down the shaft, there is a pronounced fissure. 



At the time of division, separation occurs at this pomt, pro- 

 ducing two unequal V's in the anaphase. Although the chromo- 

 somes are much shorter and thicker than in the spermatogo- 

 nium, relative proportions are preserved, and if these two parts 

 of the long chromosome (figs. 47a, 50a, pi. 6) be compared with 

 the two V's of the spermatogonium they will be found to corre- 

 spond almost exactly. That is to say, two V-shaped chromo- 

 somes of certain proportions found in the spermatogonium re- 

 appear in the first spermatocyte (united by one limb) and are 

 there separated at this point and segregated into different second 

 spermatocytes. Since one limb of one V is the accessory chromo- 

 some, it remains undivided, as usual. Attached to the accessory 

 chromosome is the rod portion of a J-shaped chromosome which 



