PLATE 



EXPLANATION OF FIGURES 



,'U to 34 are from entire follicles photographed in creasote. 



31 Follicle 1.1 mm. in long axis. X 15. The focus was changed during the 

 exposure so as to show both the upper surface and the median optical section. 

 The attached pole is up, the long axis extends right and left. The median arteries 

 (m.a.) appear on either side of the long axis (the upper one only is in focus.) 



32 View of the stigmal pole of an oocyte 2.3 mm. in long axis, showing the two 

 median arteries ending at the stigma, the boundaries of which do not appear 

 clearly. X 15. 



33 Side view of a follicle, 5.1 x 1.7 x 4.8 mm. X 8. Focus on upper side and 

 on median plane, to show the bilateral arrangement of the median artery (m.a.) 

 with reference to the long axis. 



34 Oblique stigmal pole view of the 5.47 mm. oocyte shown in fig. 7. There are 

 no capillaries in the region of the stigma (si.) 



35 Surface view of the blastodisc of an ovum taken from the middle third of the 

 oviduct at 11 p.m. and photographed by reflected light in the fixative (sublimate- 

 acetic-formol. X 6.6. Fragmentation stage of the segmental disc (s.d.), i.e., 

 an early stage in the copulation of the pronuclei. The disc and periblastic zones 

 are clearly elliptical, phl.r., periblastic ring; o.p., posterior margin of outer peri- 

 blast. 



36 Oblique surface view of the segmental disc of an egg taken from the middle 

 third of the oviduct at 11 i).m. and photographed by reflected light in the same 

 fixative as fig. 36, with one tube of a Zeiss binocular, obj. ao., oc. 2. X 15. The 

 egg was in a slightly later stage than that shown in fig. 35 and the higher magnifi- 

 cation brings out the fragmentation clearly. 



37 Two follicles, a day before ovulation, in situ. A trifle larger than natural 

 size. Tlic long axes of the follicles are oriented in the antero-posterior axis of the 

 biid. The median longitudinal section of the larger follicle is shown in fig. 37; 

 c.l, cloaca; uL, 'uterus;' inf., infundibulum. 



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