PLATE 1 



EXPLANATIOX OF FIGURES 



For abbreviations see page 256 



Fig. 1 Tangential section of the epithelium of an egg 0.75 mm. in diameter 

 from the ovary of Chrysemyspicta. Benda. Safranin and picric acid. 5/x. Xote 

 the long filamentous {l.b.) and short thick (s.b.) cytoplasmic bridges connecting 

 the adjacent cells. The intercellular substance is not stained. 



Fig. 2 Transverse section of an egg 0.69 mm. in diameter from the ovary of 

 Chrysemyspicta. Bouin. Mallory's stain. 4yu. The epithelial cells one of which 

 shows an attraction sphere (a.s.) very well are widely spaced. The terminal 

 bars (t.b.) form the anlage of the zona pellucida (i.z.p.) which is 1m in thickness. 



Fig. 3 Oblique section of the egg I'epresented in figure 2. The zona pellucida 

 {z.p.) is seen to develop from a system of large polygonal fields {pj.) marked off 

 by the terminal bars (t.b.). 



Fig. 4 Tangential section of the egg represented in figure 2. A number of 

 epithelial cells are cut through their bases, others at various heights through the 

 nucleus, a third group through the attraction sphere, a fourth through the cyto- 

 plasmic network and terminal bars at their surfaces. Central corpuscles can 

 be seen in some of the spheres. The polygonal fields (p.f.) are sharply outlined 

 by the terminal bars (t.b.). 



Fig. 5 Tangential section of an egg 0.99 mm. in diameter from the ovary of 

 Chrysemys picta. Bouin. Heidenhain's haemato.xylin, Congo red. 4^. The 

 primary network (p.n.) of the zona pellucida follows the outlines of the original 

 terminal bars and the secondarj' (s.n.) the outlines of the superficial cytoplasmic 

 network of the epithelial cells. 



Fig. 6 Tangential section of an egg 0.74 mm. in diameter from the ovary of 

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

 details are similar to those of figures 4 and 5. 



Fig. 7 Transverse section of an egg 1.1 mm. in diameter from the ovary of 

 Graptemys geographicus. Trichloracetic acid. Heidenhain's haemato.xylin, 

 Congo red. 5^. The zona pellucida has divided concentrically into two layers, 

 the inner of which shows radiating striations very clearly. It measures 3.6m 

 in thickness. 



Fig. 8 Tangential section of the egg represented in figure 7. Same fixation 

 and stain. S/x. Both layers of the zona pellucidat.i. ando.l. are seen to be formed 

 by three elements : 



1. A system of canals (c.) separated by 



2. Meshes of the fundamental substance (f.s.) which enclose 



3. Prolongations of the epithelial cells ipi\) 



254 



