The Prophase in the Ovigenesis and the Spermatogenesis of Planaria etc. 445 
the vesicle. These granules mclt together, forming au outer cap to 
the vesicle (Fig. 46 , and the staining reaction then chauges. While 
iu the granulär form it was stained brilliantly by the saffranin, it 
now, as a cap, takes the methylene blue of the triplc stain. 
Iu the meautime the archosome becomes applied to the apex of 
the nucleus, which has now become pear-shaped (Fig. 46). The 
cytoplasm of the spermatid has also leugthened out, and the remains 
of the archoplasm (a) which persist for a long time, lie in the cyto- 
plasm at the end farthest away from the head of the nucleus. 
At no time iu this stage have I beeu able to see the centro- 
somes defiuitely lying free iu the cytoplasm, but when the spermatid 
has acquired the form shown in Fig. 47, a, it is possible to make 
out a dark spot at the base of the nucleus, aud at some distance 
from it a ring shaped centrosome from which the tail of the Sperma- 
tozoon arises. 
Between the two centrosomes lies a sheath, continuous with the 
vesicular covering of the nucleus and containiug a darker central 
area (Fig. 47, b). More than this cannot be made out, owing to the 
minute size of the cell. 
For a short time the archosome is indistinguishable from the rest 
of the nucleus (Fig. 48). The latter then elongates (Fig. 49, a) and 
curves round, when the archosome again becomes evident, taking 
the stain more deeply, and liaving the appearance of a sharply pointed 
cone. 
The subsequent stages seem to indicate that by this time the 
Spermatozoon is fully formed and endowed with an individual exi- 
stence, aud that the object of the archosome is to euable it to push 
its way out of the cytoplasm / Figs. 49, 50, 51). It is very noticeable 
that the head of the Spermatozoon is bent round to one side as long 
as it is in the cytoplasm. When at last it has worked its way out 
of the latter, the Spermatozoon consists af a liead. merging indetini- 
tely into a very long tail (axial filament) Fig. 53. 
Conclusions. 
a) The synapsis, is a natural condition of the cells at a certain 
period in their history, and represents a state of condensation (not 
contraction) brought about by the turgid condition of the nucleus. 
b) The spireme iu Planaria lactea , is graduallv elaborated out 
of a reticulum, and is, in the earliest stage in which it can be 
recognised as a spireme, composed of several separate Segments. 
i 
