286 CALKINS. [Vol. XI. 



— but in all forms it is one and the same substance. It divides 

 at the beginning of nuclear activity (Figs. 12, 39 and 45), and, 

 if it occupies a distal position, each half travels around the 

 nucleus through an arc of about 90 degrees (Figs. 39, 40, 41, 

 42). This makes the axis of the spindle tangential to the 

 periphery of the central sphere, and the subsequent division 

 plane passes radially through nucleus and cytoplasm in such a 

 manner that the resulting daughter cells remain attached to the 

 blastophore. The spindle fibres are formed directly from the 

 archoplasm masses (Fig. 45). In Hermann fluid preparations 

 (teased) the archoplasm can be considered as nearly true to life 

 as is possible with this material. Such is the condition repre- 

 sented in Fig. 43, one of a large number of similar preparations ; 

 the archoplasm extends partly up the spindle fibres, and the 

 latter appear taut, as though they had been pulled from the 

 main mass. In some cases the archoplasm extends up the 

 spindle fibres as far as the chromosomes (Fig. 43). After 

 division of the chromosomes the spindle fibres seem to be in 

 part drawn back into the archoplasmic substance (Figs. 5, and 

 43 A), although I do not mean to assert that all of the spindle 

 fibres are withdrawn in this manner. 



After the reconstruction of the nucleus the archoplasm lies 

 upon the nuclear membrane like a closely fitting cap. It soon 

 becomes spherical, preparatory to redivision, but meanwhile it 

 wanders from its position at the side of the cell to the distal 

 extremity. 



I have been unable to follow the division of the archoplasm 

 in spermatocytes of the second order, although it is distinctly 

 seen at each pole of the karyokinetic spindle (Fig. 29). From 

 here it passes directly into the spermatid archoplasm, which 

 appears very distinctly, and is much more susceptible to stains 

 than at any previous period. It is the same in size as at any 

 antecedent resting-nuclear stage (Figs. 4, 12, and 35), and the 

 idea that it is of nuclear origin cannot for a moment be sus- 

 tained. It lies upon the distal part of the nuclear membrane, 

 and since after karyokinesis it lay at the side of the cell, its 

 position here can be explained only by the supposition that it 

 has moved through an arc of 90 degrees, or that the nucleus 



