DESCRIPTION OF PLATES I, II, 



Illustrating paper '' On the Existence of a Head-Kidney 

 in the Embryo Chick, and on Certain Points in the 

 Development of the Miillerian Duct/' 



Complete List of Reference Letters. 



ao. Aorta, c. v. Cardinal vein. gl. Glomerulus, gr^. First groove of 

 head-kidney, gr^. Second groove of head-kidney, gr^. Third groove of 

 head-kidney, g. e. Germinal epithelium, mr. b. Malpighian body. me. 

 Mesentery, m. d. Miillerian duct. r-^. First ridge of head-kidney, r^. 

 Second ridge of head-kidney, r^. Third ridge of head-kidney. W. d. 

 Wolffian duct. x. Fold in germinal epithelium. 



EXPLANATION OF PLATE I. 



Series A. — Sections through the head-kidney at our second stage. 

 Zeiss, 2, ocul. 3 (reduced one third). The second and third grooves are 

 represented with the ridge connecting them, and the rod of cells running 

 backwards for a short distance. 



No. 1. — Section through the second groove. 



No. 2. — Section through the ridge connecting the second and third 

 grooves. 



No. 3. — Section passing through the same ridge at a point nearer the 

 third groove. 



Nos. 4, 5, 6. — Sections through the third groove. 



No. 7. — Section through the point where the third groove passes into 

 the solid rod of cells. 



No. 8. — Section through the rod when quite separated from the germinal 

 epithelium. 



No. 9. — Section very near the termination of the rod. 



No. 10. — Last section in which any trace of the rod is seen. 



Series B. — Sections passing through the head- kidney at our third stage. 

 Zeiss, c, ocul. 2. Our figures are representations of the following sections 

 of the series, section 1 being the first which passes through the anterior 

 groove of the head-kidney. 



No. 



Section 



3. 



4. 



5. 



6. 



8. 

 10. 

 11. 



No. 



8 



. Section 13. 



9 



15. 



10 



16. 



11 



17. 



12 



18. 



13 



19. 



14 



20. 



The Miillerian duct extends through eleven more sections. 



The first groove {g)\.) extends to No. 3. 



The second groove (^rj.) extends from No. 4 to No. 7. 



The third groove {gr^.) extends from No. 11 to No. 13. 



The first ridge (rj.) extends from No. 2 to No. 5. 



The second ridge {r^.) extends from No. 8 to No. 11. 



The third ridge {r^.) extends from No. 13 backwards through twelve 

 sections, when it terminates by a pointed extremity. 



Fig. C. — Section through the ridge connecting the second and third 

 grooves of the head-kidney of an embryo slightly younger than that from 

 which Series B. was taken. Zeiss, c, ocul. 3 (reduced one-third). 



The fold of the germinal epitiielium, which gives rise to a deep groove 

 {x.) external to the head-kidney is well marked. 



Series G. — Sections through the rod of cells constituting the termina- 

 tion of the Miillerian duct at a stage in which the head-kidney is still 

 present. Zeiss, c, ocul. 2. 



