216 Proceedings of the Royal Physical Society. 
the first time, and the nuclei all become altered in appearance. Much of the 
chromatin which has been so apparent in previous stages appears to con- 
centrate in blocks on the nuclear membrane, and the nucleus in consequence 
becomes more ringlike in optical section while the karyosome is much 
diminished in size (compare Pl. VIII. Figs. 10 and 11). These alterations are 
correlated apparently with the specialisation in function which the nuclei 
now display, and render it fairly easy to distinguish between the nuclei, but 
at the same time make it much more difficult to determine the part played in 
the formation of the fully developed spore by the original pair of small nuclei. 
The pair of pansporoblast nuclei become slightly, and the two pairs of spore 
nuclei (PI. VIII. Fig. 11, b) considerably, hypertrophied. The amoebula nuclei 
(“ Amoboidkeimkerne ”) (Pl. VIII. Fig. 11, a), of which there is one pair in each 
spore, seem at this stage each to consist in optical section of a ring of 
chromatin dots with a central small karyosome. The two amoebula nuclei 
in each spore are closely associated, and it is not easy always to distinguish 
one from the other. The four polar capsule nuclei (P]. VIII. Fig. 11, ¢) in each 
spore are alike, and are very different from the amoebulz or spore nuclei, 
while near each can be seen sometimes a vacuole, the future polar capsule. 
When the spore is fully developed its walls become resistant, and it is 
difficult to see the different nuclei (Plate VIII. Fig. 12). The polar capsules 
are seen to form two pairs, one long and one short pair. It should be 
remembered that the spore is a bivalved structure, one valve to each spore 
nucleus, as shown by the divergent tails of the spore (Fig. 12); and transverse 
sections show that each valve has one short and one long polar capsule, as 
indicated by the different sectional area of the capsules. The sutural ridge 
between the two spore valves is also well shown in such sections, 
DESCRIPTION OF PuatEe VIII. 
All figures are reproduced at a magnification of x 3000, except where otherwise stated. 
Fig. 1. Cyst in testis-follicle of Lepidosiren paradoxa showing clump of spores. x 270. 
2and 3. Microcytes, 
4. Megalocyte. 
5. Fusion of micro- and megalo- cyte to form sporoblast, 
6. and 7. Union of two sporoblasts before fusion of micro- and megalo- cyte is 
completed. 
8. Fusion of two sporoblasts forming pansporoblast. 
», 9. Pansporoblast in six-nucleate stage. 
10. 69 eight- 5 
11. Two fully formed spores in pansporoblast. 
12, Mature spore. x 1500. 
