EXPLANATION OF THE PLATES. xvii 



Fig. IG. Tlace cells from the kidney oi Jldlx cupersa. The contained 

 Becretion is dead white, and presents a chalky apjitarance. 



Fig. 17. Two cells iioiu the vesicles of the testicle of Squalus cornubicua. 

 The contained bundles of spermatozoa are developed from 

 the nucleus — each spermatozoon being a spiiiil cell. 



Plate V. page 412. 



Fig. 1. Five cells from the mamma of the bitck In addition to their 

 nuclei, these cells contain milk-gh^bules. 



Fig. 2. A portion of duct from the testicle of t^'juuhis cornnhlcux. A 

 f(!W nucleated cells, the jmmary or germinal cells of the 

 future acini, are attached to its walls. 



Fig. 3. Tlie primary cell of an acinus in a more advanced stage. Tlie 

 nucleus has produced a mass of young cells. Tlie pedicle 

 appears to have been formed by the germinal cell carrying 

 forward the wall of the duct. A diaphragm accordbigly 

 presents itself across the neck of the pedicle. 



Fig. 4. A primary cell in a more advanced stage. 



Fig. 5. A primary cell still more advanced. 



Fig. G. Some of the secondary cells, products of the nucleus of the 

 primary cell, are cylindrical, and are arranged in a spiral. 



Fig. 7. The change into cylinders, and the spiral arrangement com- 

 pleted. 



Fig. 8. a. One of the secondary cells ; its nucleus a mass of young cells. 

 h. A secondary cell elongated into a cylinder, each cell of its 

 composite nucleus elongated into a spiral c. The spiral cells 

 or spermatozoa, free. 



Fig. 9. A bunch of acini, in various states of development, maturity, 

 and atrophy. 

 The four follo\nng figures are diagrams, arranged so as to illus- 

 trate the intimate nature of the changes which occur in vesi- 

 cular glands when in a state of functional activity. 



Fig. 10. A portion of gland-duct with two acini. One of the acini is 

 a simple primary cell ; the other is in a state of develop- 

 ment, its nucleus producing young cells. 



Fig. 11. Both acini are advancing; the second has almost reached 

 maturity. 



Fig. 12 The second acinus is ready to pour out its contents, the first 

 to take its place. 



Fig. 1 3. The second acinus is in a state of atrophy, the first is rijK*. 



Fig. 14. Two follicles from the liver of Carcinus nutiins. Tlie colour- 

 less gt rminal spot is at the blind i-xtremity of the follicle. 

 Tlie secreting cells become distended with bile and oil as 

 they recede from the germinal spot. 



