348 
HERBERT H. BROWN. 
Dr. Heneage Gibbes 1 has observed a spiral filament in the 
spermatozoa of several animals, e. g. horse, guineapig, and 
bull, which presents a somewhat similar appearance to that 
which I have just described; he considered this to correspond 
to the so-called spiral filament of the newt’s spermatozoon, 
which is an undulating filament attached to the spermatozoon 
by a fine membrane, which acts as a mesentery ; but it is 
difficult to see much resemblance between the spiral filament 
which is stained by the gold method, and is confined to the 
middle piece of the spermatozoon, and the long undulating 
filament of the spermatozoon of the newt. I have not yet 
looked for this spiral filament in the middle piece of the 
spermatozoa of other animals, but will endeavour to do so 
during the present summer. 
History of the Process of Spermatogenesis. — Hav- 
ing thus briefly described the various elements of the seminal 
tubule, I shall proceed to trace out continuously the history 
of the origin and development of the spermatozoa. 
The process is a continuous one, i. e. a new crop of cells 
makes its appearance near the basement membrane as each 
successive crop of ripe spermatozoa leaves the tubule ; and in 
a section of a single tubule four or five generations of cells at 
different stages of their development are contained, so that 
the entire process of spermatogenesis occupies a corresponding 
number of cycles. An entire cycle is represented by figs. 1 to 
10. During this period a crop of spermatozoa leaves the 
tubule, their place is taken by a similar crop into which the 
young spermatozoa with spherical nuclei of the third layer have 
developed, the growing cells of the second layer produce by 
their division another generation of young spermatozoa, the 
small growing cells of the outer layer increase in size and 
become the large cells of the second layer, and a new crop of 
young growing cells makes its appearance in the outer layer. 
Thus, during a single cycle each of the layers described has 
moved forwards one stage, and the entire process of develop- 
1 ‘Quart. Journ. Mic. Sci.’ 
