ABBREVIATIONS 



a. p., area of proliferation 



U.S., attraction sphere 



c, canals 



C.C., central corpuscle 



C.71., cytoplasmic network 



ep., epithelium 



f.s., fundamental substance 



i.l., inner layer 



i.z.p., incipient zona pellucida 



k.e., knob-like enlargements 



Lb., long bridges 



O.I., outer layer 



p.f., polygonal fields 



p.n., primary network 



/;;•., prolongations 



r.s., radiating striations 



s., outer stratum 



s', middle stratum 



s", inner stratum 



s.b., short bridges 



s.n., secondary network 



t.b., terminal bars 



y., yolk 



z.p., zona pellucida 



The figures are not reduced in reproduction. They are microphotographs 

 taken at a magnification of 750 diameters. Leitz microscope. Obj.7. Oc. 1. 



PLATE 2 



EXPLANATION OF FIGURES 



Fig. 9 Transverse section of an egg 1.42 mm. in diameter from the ovary of 

 Clemmys guttatus. Benda. Safranin and picric acid. 5/u. The outer layer 

 (o.l.) of the zona has thickened to a greater extent than the inner (i.l.). The pro- 

 longations show knob-like enlargements at their tips {k.e.)t The area of pro- 

 liferation (a. p. ) is deeply stained. Zone measurement 12^. 



Fig. 10 Transverse section of an egg 2.6 mm. in diameter from the ovary of 

 Chrysemys picta. Bouin. Heidenhain's haematoxylin. Congo red. 4/^. The 

 prolongations (pr.) are clearly seen extending from the scant cytoplasm of the 

 epithelial cells down into the outer layer. The zona measures 17^ in thickness. 



Fig. 11 Oblique section of the egg represented in figure 10. Same fixation 

 and staining. 4^. Note the canals and the prolongations of the epithelial cells. 



Fig. 12 Tangential section of the egg represented in figures 10 and 11. Bouin. 

 Mallory's stain. 4m. With figures 10 and 11 this shows the great increase in 

 thickness in both layers of the zona (cf. with figure 8). 



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