Trow . — The Karyology of Saprolegnia. 65 1 
b and c. Radial amd tangential sections respectively of the lower portion of 
a younger sporangium. The strands of protoplasm connecting the young spores 
are well seen, xiigo. 
Fig. 4. Median section, 7*5 p thick, of a young oogonium which contained 
72 nuclei. Its diameter was 29 x 1150. 
Fig. 5. Median section of an oogonium. The basal wall has been formed. 
Three of the antheridia attached to it are also represented. The nuclei are 
preparing for the reducing division, x 660. 
Fig. 6. a, c, d, and e. Nuclei undergoing the reducing division. In d the 
half chromosomes are seen in plan and in e in profile. The early stages are 
represented in a and b. The nuclear wall appears to be breaking down in e and 
the nucleo-hyaloplasm is dispersing itself in the surrounding protoplasm, 
x 2300. 
Fig. 7. An oblique section of the oogonium in which the nuclei of Fig. 6 were 
found. The antheridia were not drawn. The two half chromosomes are seen in 
most of the nuclei. The intact nuclear wall appears still to prevent the escape of 
the nucleo-hyaloplasm into the surrounding protoplasm, x 1150. 
Fig. 8. a and b. Dividing nuclei from an oogonium, c and d. Dividing nuclei 
from an antheridium. The half chromosomes lie more or less free in the 
protoplasm. * x 2300. 
Fig. 9. Median section of an oogonium, one of the antheridia attached to which 
is also drawn. The nuclei are in the condition represented in Fig. 8, and the 
stained masses of nucleo-hyaloplasm and microsomata are still evident, x 1 1 50. 
Fig. 10. a and b. Two sections of one oogonium and sections of two antheridia 
showing the completion of the development of the gameto-nuclei (the end of the 
reducing division) and the commencement of the degeneration of the rejected 
gameto-nuclei. x 1 1 50. 
Fig. 11. a and b. Tangential and median sections of an oogonium (antheridia 
not drawn) which had a diameter of 50 [i and contained 46 gameto-nuclei. The 
oogonium was in the typically vacuolated condition, x 1 1 50. 
Fig. 12. a and b. Tangential and nearly median sections of an oogonium 
(antheridia not drawn) at the stage preceding the commencement of the formation 
of the oosphere rudiments, x 1 150. 
Fig. 13. Three successive sections of an oogonium (antheridia not drawn) with 
three oosphere-rudiments in the earliest stage of development. Degenerate fusion- 
nuclei are to be noted in these, but only three typical gameto nuclei, one near the 
centre of each rudiment, x 1 150. 
Fig. 14. Section of an oogonium with one uninucleate oosphere-rudiment. The 
three remaining sections contained three additional uninucleate rudiments, 
x 1150. 
Fig. 15. Section of an oogonium with 4 nearly mature uninucleate oospheres. 
The antheridium is proceeding to develope a fertilization-tube, x 1100. 
S. dioica , De Bary. Fertilization. 
Fig. 16. Section of a large oogonium (antheridia not drawn) with three 
uninucleate oosphere-rudiments. All the other rudiments in the oogonium were 
likewise uninucleate, x 610. 
Fig. 17. Median section of a large oogonium with mature oospheres. The 
spongy character of the protoplasm is beautifully seen and also the single central 
Y y 2 
