350 
HERBERT H. BROWN. 
into an irregular skein of filaments (fig. 2, b'). In this con- 
dition they increase in size without dividing, and gradually 
leave the wall of the tubule, until by the division of the spore- 
cells and formation of a new crop of cells between them and 
the basement membrane, they come to form the second row 
(fig. 8, b '). By the time the stage of fig. 1 is reached the nuclei 
of these cells have attained their full size, but the protoplasm 
continues to increase in amount. The nuclei are spherical and 
large (diam. 10 fi), and present the appearance represented in 
the figure (fig. 1, b"). A large granule — the accessory cor- 
puscle — which stains darkly with chloride of gold, is embedded 
in the protoplasm near the nucleus (fig 12, b"). Even at the 
stage of fig. 1 a cell is occasionally seen containing tw’O nuclei, 
one being placed internal to the other ; apparently all the cells 
when their growth is completed divide into two, though the 
nuclei do not as yet show any further karyokinetic changes, so 
that at a later stage the cells are arranged in a double row. 
Sometimes a nucleus may be seen apparently in the act of 
dividing, and cells containing two nuclei become more frequent 
(fig. 5, b") ; and now the growing cells having reached their full 
development, divide by karvokinesis, the phenomena of which 
may be very well observed, and give to a tubule in this stage 
a very characteristic appearance (PI. XXII, fig. 6, b'"). The 
astral and diastral forms can be readily recognised, and, viewed 
in profile, the achromatic filaments may also be seen. (Fig. 6 
represents the appearances presented by these cells under a 
magnifying power of about 750 diameters.) In chloride of 
gold preparations the accessory corpuscle appears to become 
broken up during karvokinesis ; perhaps it forms the accessory 
corpuscles of the young spermatozoa, and some small granules 
wdiich stain slightly with hgematoxvlin and appear to be pro- 
duced during karvokinesis may represent this process. 
It appears that the cells which result from the karyokinetic 
division of a growing cell do not separate from one another 
entirely, but remain at first united in groups by a very small 
amount of the protoplasm of the mother cell. The outlines 
of the cells of which these groups are composed cannot be 
