No. 2] THE OOGENESIS OF BUFO LENTIGINOSUS. 301 
part, although they are not connected in any way. The threads 
do not present the clear cut, granular appearance of the 
spireme shown in Fig. 26, as they have a jagged outline and 
send out fine projections on either side. 
There is absolutely no uniformity in the arrangement of the 
chromatin threads after the splitting of the spireme. At times 
the sister threads seem to lie close together throughout their 
whole extent (Fig. 30) ; again the sister portions of the spireme 
lie parallel for a short distance and then become widely scat- 
tered throughout the nucleus (Fig. 31); in rare cases, as 
shown in Fig. 32, the chromatin threads are as evenly dis- 
tributed throughout the nucleus as they are at the stage shown 
in Fig. 27, and there is nothing except the size of the nucleus 
and the character of the threads to indicate that there has 
been a splitting of the spireme. I am very sure that such a 
condition-of the chromatin as that shown in Fig. 32 could 
not have been brought about by a gradual lengthening of the 
spireme, since the great majority of nuclei intermediate in 
size between that of Fig. 27 and that of Fig. 32 appear similar 
to those shown in Figs. 28-31. 
Soon after the stage of Fig. 30 the spireme breaks trans- 
versely, forming, in most cases, long double segments which 
vary considerably in length (Figs. 33, 34, 36, 37). The sister 
portions of the segments may lie parallel or they may be 
intertwined in various ways; they may be united at one or at 
both ends, forming a figure 8 or an oval ring; in other cases 
both ends of the segments are free and the threads cross in 
the form of an X or a Y. The condition of the chromatin 
threads shown in Figs. 30-34 is found in nuclei having a 
diameter of 0.015-0.02 mm. 
I have tried to reconstruct a nucleus in the stage of devel- 
opment shown in Figs. 33-34, by placing together a series of 
camera drawings of all of the sections of the nucleus, in the 
hope that I might be able to determine by this means the total 
number of chromatin segments. Owing to the fact that the 
segments are of different lengths and that they are united in a 
great variety of ways, it has been very difficult to arrive at any 
