60 THOS. H. MONTGOMERY jr., 



have side views of the chromosomes, to view them from the pole of 

 the original spindle (Figs. 203—205, 207 — 212). By continued tension 

 of the mantle fibres they all come to lie parallel to one another, in 

 such a way, that the plane of their transverse constrictions is per- 

 pendicular to the axis of the tertiary central spindle (Figs. 213 — 217). 

 At this stage the chromosomes often lie so densely that they can 

 hardly be distinguished from one another (Fig. 202), but they do not 

 fuse together, as this figure would indicate, but all persist as separate 

 elements, that is, it is only a case of close apposition. 



The appearance of the transverse constrictions on the daughter 

 chromosomes, which may frequently be noted while the latter are still 

 parallel to the axis of the original spindle (Figs. 194, 196 — 198), and 

 then the easily observable torsion of the longitudinal axes of the 

 chromosomes through an angle of 90 '', proves that these constrictions 

 are truly transverse ; and hence, that the second spcrmatocytic division, 

 like the first, results in transverse (reduction) divisions of the 

 chromosomes. It might be objected, that though the daughter 

 chromosomes become elongated and constricted in the metakinesis, 

 nevertheless, by the tension of the mantle fibres, when the two 

 centrosomes are situated at right angles to the original spindle, the 

 chromosomes subsequently become elongated in the opposite (trans- 

 verse) direction, so that their ultimate transverse constrictions, though 

 perpendicular to their longitudinal axes, would correspond morpho- 

 logically to longitudinal constrictions. This objection, however, is met 

 by the facts found: the early appearance of the constrictions in 

 numerous cases, and the subsequent gradual torsion of the chromo- 

 somes through an angle of 90*^. I carefully examined this point, since 

 I expected to find that the 2nd spcrmatocytic division would be 

 equational; but all appearances show that the process is as I have 

 described it (Figs. 190-201, 203—206, in all of which the chromo- 

 somes have been accurately drawn with the camera lucida). 



The 1st spcrmatocytic division is thus a transverse (reduction) 

 division, and so is the 2nd. Each 2nd spermatocyte receives 7 

 daughter chromosomes, this number being found in all cases when 

 the chromosomal plate is viewed from the pole of the original spindle 

 (Figs. 207 — 212). In a few cases, so few that they must be con- 

 sidered abnormal, a whole undivided chromosome passes into a 2nd 

 spermatocyte, but I have met with only two or three such cases. 

 Henking found in Fyrrhocoris ('90 b), and later ('92) in some other 

 cases, that the 2nd spermatocytes receive an unequal number of 



