334 
Dì L. SOÓS 
into a larger one, as a rule, which lies nearer the hind part of the 
nucleus, and a smaller one lying nearer the nucleus. The two centrioles 
seem at first glance to be whole discs, in reality, however, they are 
perforated at their centre, as ?s shown on their cross sections (PL XL, 
Fig. 18.). I have not had the opportunity of establishing when the 
distale centriole gets divided into two parts, and when they become 
perforated. The first question seems to be of minor significance, the 
latter is, however, very important in consequence of its connection with 
the origin of the axial filament. 
The spermatid afterwards elongates still more. Its nucleus is first 
hemispherical (PL XL, Figs. 11., 12.), then cylindrical (Fig. 13.), and 
it takes up a position at the fore end of the spermatid. The cytoplasm 
which had till then also surrounded the nucleus retires backwards, 
and thus it remains uncovered at the end. On Figs. 11. and 12., PL 
XL, cases are to be seen where the nucleus, is connected with the 
cytoplasm only by means of the centrosphere. The perforatorium is in 
this stage perfectly formed, and it does not differ from that of the de¬ 
finitive spermatozoon at all (Fig. 13.). 
On Fig. 14., PI XL, a spermatid is figured in a very advanced 
stage of development. The nucleus has already assumed its definitive 
form, i. e. it has transformed itself into the head of the spermatozoon. 
The cytoplasm forms behind the head a thin sheath around the axial 
filament, in the posterior part, however, is present more abundantly. 
The nebenkern has disappeared, and the number of the mitochondria 
granules has also diminished, and the present ones grouped together at 
the end of the cell. 
The head of the definitive spermatozoon is either straight, conic 
in shape, or it is arcuated or turned in a spiral line (PL XI., Figs. 
16., 17.). Its anterior end is occupied by the perforatorium. At the 
opposite end of the head the centrosome is to be found which is not 
to be seen from the side, since it has retired into the mentioned 
hollow of the head, but is well visible in spermatozoa lying oblique to 
the optical axis of the microscope. 
The tail of the spermatozoa consists of the axial filament and of 
an extremely fine sheath of cytoplasm surrounding it (Fig. 17.). The 
cytoplasm cover is always present in intact spermatozoa, therefore 
Bolles Lee’s statement that the spermatozoa have no cytoplasm, must 
be regarded as incorrect. The tail is very long, and has the same thick¬ 
ness along its whole length. The distale centriole or centrioles, are 
lacking in the spermatozoa. About their disappearance nothing is known 
to me. 
