24 ATLAS OF BIOLOGY. 



FIG. XXIII. Three figures illustrating the structure of the kidney. 



i. Portion of a section. Alcohol and borax carmine. D. 4. 



The blood-vessels indicated are generally full of corpuscles not here drawn. 



ii. The ventral surface of a portion of the right kidney after removal of the peritoneum. 

 Slightly magnified. 



The small oscula3 represent the apertures of communication (uephrostomes) between 

 the uriniferous tubules and the body-cavity. For details see Spengel (22). 



iii. A glomerulus from a section of the kidney injected from the dorsal aorta. See 

 Appendix D. Alcohol. D. S. 



FIG. XXIV. Transverse section of skin. Alcohol and borax carmine. D. 3. 

 Of the two cutaneous glands figured, the left hand one is represented en face. 



FIG. XXV. Two young ovicells with their investing follicular epithelium. Alcohol 

 and borax carmine. D. 2. 



i. Optical section, ii. Surface view. 



The young ovicells such as are here figured, may be easily identified by the absence of 

 that pigment so characteristic of the ripe ovum (see PI. VI ) They are very small and 

 quite white, and do not always completely fill the follicle as did the one drawn in section 

 above. 



For figure of a section of the Frog's ovary see Marshall (16). 



Fig. XXVI. Spermatozoa, obtained by teasing up a small portion of the testis. 



The head is often carried as at *, thus giving rise to very deceptive appearances. Of 

 the spermatozoan aggregates figured, that of the left side had attached to it a cell of the 

 germinal epithelium. See Bloornfield (1). 



a. Artery. 



a. i- . Axis fibre. 



b.m. Muscle bundle (fasciculus). 



b.n. Nerve bundle. 



b.v. Blood vessels. 



c. Cones. 



c.a. Anterior cornu. 



c.b. Bile capillaries. 



c.B. Bowman's capsule. 



e.c. Canalis centralis. 



c.ep. Ciliated epithelium of t)ic same. 



c7. Cilia. 



.cp. White corpuscles, 



Ci>\ .Red corpuscles, 



Posterior cornu. 



Bone corpuscle. 



Cartilage corpuscle. 



Muscle corpuscle. 



Nerve corpuscle. 



Connective-tissue corpuscle. 



Blood capillaries. 



Derma. 



Muscular layer of derma. 



Pbragmodisc (septal zone). 



Sarcodisc (interseptal zone). 



Superficial horny layer of epiderma. 



Middle layer of epiderma. 



Columnar (Malpighian) layer of epiderraa : 



