EXPLANATION OF FIGURES 



The figures illustrating this article were drawn by Mr. A. B. Streedain. 

 Zeiss apochromatic objective 1.5 mm., and compensating ocular 6 were employed 

 for all figures except no. 3, for which Zeiss 8.0 mm. objective and ocular 8 were 

 used. The camera lucida was employed for all the figures and magnification 

 calculated at table level in all cases. The figures were reduced by one-fourth in 

 reproduction giving a magnification of 1125 diameters for all the illustrations 

 except figure 3, which has a magnification of 205 diameters. The figures were 

 drawn from preparations fixed in Bensley's acetic-osmic-bichromate mixture and 

 stained with Bensley's anilin acid fuchsin-Wright's blood stain. All the sections 

 were cut 4^ in thickness. 



alb., albuginea 



at.s'p., attraction sphere 



ex., cortical cord or cord of second 



proliferation 

 coelom, coelomic cavity 

 f.c, deep indifferent cell or follicular 



cell 

 germ.ep., germinal epithelium 

 l.gon., left indifferent gonad 



iti.c, medullary cord or cord of first 



proliferation 

 vied., medullary region of ovary 

 ■Dies., mesentery 

 oog., oogonia 



pr.u., primordial genn-cell 

 pr'.o'., primordial germ-cell in state of 



division 

 r.gon., right indifferent gonad 





germep. 7/>^^"^^ - =^-^"(--l': -.Y 



fi 







'■;3 



A'. $'■ 



Fig. 1 Portion of a transverse section through anterior third of Wolffian 

 bodies of a 3f-day chick embryo. This section shows the appearance of the 

 germinal epithelium just after its formation, the position and characteristics of 

 the primordial germ-cells, and the tissue beneath the epithelium. 



451 



