JOURNAL OF MICROSCOPICAL SCIENCE. 



DESCRIPTION OF PLATES I, IL 



Illustrating Messrs, Balfour and Sedgwick's paper *'0n the 

 Existence of a Head-Kidney in the Embryo Chick, 

 and on Certain Points in the Development of the 

 Miillerian Duct.'' 



Complete List ok Reference Letters. 

 ao. Aorla. c.v. Cardinal vein. ffl. Glomerulus, gi\. Eirst groove of 

 iiead-kidney. gr.^. Second fjroove oT liead-kidney. gr^^. Third groove of 

 iiead-kidney. g. e. Germinal epithelium, mr. h. Maipighian body. me. 

 Mesentery, m. d. Miiilerian duct. Tj. First ridge of head-kiduey. r,. 

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

 Wolffian duet, 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 witii the ridge connecting them, and the rod of cells running 

 backwards for a sliort 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. 1 . . . Section 3. No. 

 „ 2 . . . „ 4. 



„ 3 5. 



„ 4 . . . „ 6. 



5) 5 . . . „ 8. 



„ 6 . . . „ 10. 



„ 7 . . . „ n. . 



The Miillerian duct extends through eleven more sections. 



The first groove {gr^?^ extends to No. 3. 



The second groove (g)\ ) extends from No. 4 to No. 7. 



The third groove ((^rg.) extends from No. 11 to No. 13. 



The first ridge {r^?j extends from No. 2 to No. 5. 



The second ridge (fj.) extends from No. 8 to No. 11. 



The third ridge (j-^.) 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 epithelium, 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-kiduey is still 

 present. Zeiss, c, ocul. 2. 



