164 
Kathaiine Foot and E. C. Strobell 
Photo 4. A bouquet stage in wHch a few of the cliromosonies have separated 
from the stem of the bouquet. 
Photo 5. A bouquet stage with all the cliromosomes spread apart fiom the 
stem. There appear to be oidy 10 chromosomes in this group, but the long chromo- 
some on the right periphery must represent 2 bivalents attached end to end. 
Photo 6. A later stage than photo 5. The thin leptotene tlrreads shown in 
this preparation, and in photos 7 and 9 are found in the stages that occur between 
the bouquet stage, showTi in photo 5, and the resting oöcytes of photos 8 and 10. 
These threads evidently represent the attenuation of the earher pachytene bivalents. 
Photo 7. The contraction phase of the leptotene stage. A nucleolus is tj^ji- 
cally present at this stage and also frequently found in the bouquet stage. 
Photo 8. The nucleus of a young resting oöcyte. The transitional sizes can 
be easily followed between the oöcjTes at tliis stage and those that have reached their 
maximum growth at the free end of the ovary. See text-figure. 
Photo 9. About the same stage as photos 6 and 7 — but in this preparation 
the thin leptotene threads are spread A\ide apart. 
Photo 10. The nucleus of a growing oöcyte showing the chromatin reticulum 
and a large nucleolus. 
Photo 11. Germinal vesicle from a much larger oöcyte near the distal end of 
the ovary. This germinal vesicle has not yet reached its maximum size. Many of 
the germinal vesicles in the eggs at the free end of the ovary are often fuUy as large 
as the one shown in photo 12, wliich is from an egg found in the receptaculum ovorum. 
Photo 12. A germinal vesicle of an egg from the receptaciüum ovorum. At 
this stage both the large and small nucleolus are present and the chromatin is more 
or less eveiüy distributed tliroughout the nucleus. 'fhe first step in the evolution 
of the chromosomes is the appearance of an exceedingly dehcate cliromatic tlrread, much 
more dehcate than the thread shown in photo 13. 
Photo 13. A germinal vesicle of an egg from the receptaculum ovorum, show- 
ing the chromatin at the leptotene stage. The long thin twisted threads represent 
the reverse process shown in photo 7, the stage at wliich the leptotene threads dis- 
appear b e f o r e the rest stage while in photo 13, the threads are just emerging a f t e r 
the long growth period. The large nucleolus has broken and is spread over a larger 
area than usual. 
Plate Xn. 
Photo 14. A germinal vesicle of an egg from the receptaculum ovorum, showing 
a httle later stage than photo 13. Both the large and small nucleolus are present. 
The leptotene threads are thicker and in some places they show the longitudinal spht 
characteristic of the later stages. See Foot and Strobell (05) — photos 114 and 115. 
Photo 15. A germinal vesicle of an egg from the receptaculum ovorum, sho\nng 
thicker chromatin threads — ‘The pachytene stage”. We have never found the tlureads 
at tliis stage oriented in any form resembUng the bouquet stage. The longitudinal 
spht typically seen at tliis stage, is not clear in this preparation. The large and small 
nucleolus are present, and in dose contact. 
Photo 16. A germinal vesicle of an egg from the receptaculum ovorum, showing 
the cluomatin at the diplotene stage. It is eddent the bivalents are longitudinaUy 
spht and many of them show the point of their transverse division, wliich occurs in the 
