The Prophase in the Ovigenesis and the Spermatogenesis of Planaria etc. 439 
As said before, concurrently with the increase in size of the 
definite ova, the „secondary” ova become smaller. It is probable that 
the great part of tlieir substance passes over to tlie delinite ova by 
osmosis. 
In Planaria torva, Mattiesen finds tbe nucleolus disappears 
shortly after tlie synapsis. Here on tbe contrary, the nucleolus is 
plaiuly visible right through the prophase. Before going any further, 
it is necessary now to refer to Schleip’s results with Planaria gono- 
cephala ('06). Possibly, owing to the small scale on whicli bis figures 
are drawn, a greater difi'erence than really exists, appears between 
bis figures of tbe leptotene nuclei and mine. But I have totally failed 
to find anything in PL lactea , coinparable to bis figs. 11 and 12 of 
zygotene nuclei. In these, especially fig. 11, two sorts of segments 
are sharplv contrasted, one twice as thick as the otlier. As far as 
PI. lactea is concerned, it certainlv caunot be said that „niemals 
finden wir irgend welche Zwischenstufen in der Dicke des Fadens”. 
On the contrary, a glance at fig. 1, plate I, is sufficient to show that 
all the segments are not of even tbickness, some segments have gone 
a degree further in condensation than others. 
At the earliest stage (Fig. 4) in whicli they are definitelv appa- 
rent, the spireme segments are very long and take manv turns round 
the nuclear cavity, and therefore it is not possible to count them with 
certainty. But iu the commenceinent of, and during the synapsis, it 
is clearly evident, with a little careful manipulation of the fine ad- 
justment, that there are 8 segments, and therefore we may justly 
assume that from the very commencement of its formation the spireme 
is composed of 8 separate segments. In order to see tliis, it is 
necessary to cut the sections at least 14 u. thick, so as to take in 
the whole of the nucleus in one section, and it is possible that 
Schleie failed to do so, on account of the thinness of bis sections 
whicli he puts at 7,5 <x. In such thick sections, it is quite easy to 
see that the spireme segments make several turns round the nuclear 
cavity (see figs. 4 and 5), and therefore when they are cut across 
transversely, one naturally sees, as in Schleip’s fig. 8, more than 
16 free ends, but this is no justification for the assumption that in 
the leptotene nuclei there are 16 separate segments, whicli pair up 
longitudinally later on to 8. 
These conclusions are in striking agreement with those of Gold- 
schmidt ('08) on the early stages of the maturation of the oocytes in 
Dicrocoeliwn lanceatum. Indeed, the only difference is that I have 
