EXPLANATION OF THE PLATES. 201 



FIG. III. Epithelial cells from the epididymis. 



FIG. IV. Human spermatozoa. 1, Head of a spermato- 

 zoon ; 2, its caudal prolongation. 



FIG. V. Development of spermatozoa, as observed in 

 the Guinea pig. 1, Epithelial cell with a solitary nucleus; 2, 

 epithelial cell with two nuclei ; 3, the head of the spermatozoon 

 making its appearance in the periphery of a nucleus ; 4 and 5, 

 two other cells inclosing a larger number of nuclei in the same 

 stage of development ; 6, nuclei in which the caudal prolonga- 

 tion (7) of the spermatozoon is visible ; 8, a nucleus with its 

 spermatozoon uncoiled ; 9, free spermatozoa. 



FIG. VI. Ovisac. 1, stroma of the ovisac ; 2, membrana 

 granulosa of the ovisac ; 3, its proligerous disc ; 4, zona pellu- 

 cida of the ovule ; 5, yelk ; 6, germinal vesicle ; 7, germinal 

 spot. 



FIG. VII. Ovisac containing two ovules, 1 and 2. 



FIG. VIII. An ovule in which the process of segmen- 

 tation has taken place. 1, Zona pellucida ; 2, segmenta- 

 tion of the vitellus. 



PLATE XXII. 



LIVER. SPLEEN. TPIYKOID GLAND. 



FIG. I. Vena portse of the hog magnified 50 diameters. 



1, A lobule of the liver; 2, interlobular branches of the vena 

 portce / 3, their subdivisions ; 4, capillary network. 



FIG. II. Human vena portse (from a child three years of 

 age)', magnified 50 diameters. 1, Branches of the vena portce / 



2, their termination in the capillary plexus. 



FIG. III. Intra-lobular vein of the rabbit magnified 50 

 diameters. 1, Boundary of a lobule ; 2, trunk of the vein ; 3, 

 capillary network. 



FIG. IV. Hepatic cells. 1, Large cells; 2, small cells. 



FIG. V. Epithelial cells from the mucous membrane of the 

 gall-bladder. 



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