EXPLANATION OF THE PLATE. 305 



EXPLANATION OF THE PLATE (VIII). 



Fig. 1. Four secreting cells from the ink bag of Loligo sagittata. 



Fig. 2. Five cells from the liver of Patella vulgata. In this instance the bile is contained in the cavi- 

 ties of the secondary cells, which constitute the nucleus of the primary cell. 



Fig. 3. Three cells from the kidney of Helix aspersa. The contained secretion is dead white, and pre- 

 sents a chalky appearance. 



Fig 4. Two cells from the vesicles of the testicle of Squalus cornubicus. The contained bundles of 

 spermatozoa are developed from the nucleus, each spermatozoon being a spiral cell. 



Fig. 5. Five cells from the mamma of the biteh. In addition to their nuclei, these cells contain milk 

 globules. 



Fig. 6. A portion of duct from the testicle of Squalus cornubicus. A few nucleated cells, the primary 

 or germinal cells of the future acini are attached to its walls. 



Fig. 7. The primary cell of an acinus in a more advanced stage. The nucleus has produced a mass of 

 of young cells. The pedicle appears to have been formed by the germinal cell carrying forward the 

 wall of the duct. A diaphragm accordingly presents itself, across the neck of the pedicle. 



Fig. 8. A primary cell in a more advanced stage. 



Fig. 9. A primary cell still more advanced. 



Fig. 10. Some of the secondary cells, products of the nucleus of the primary cell, are cylindrical, and 

 are arranged in a spiral. 



Fig. 11. The change into cylinders, and the spiral arrangement completed. 



Fig. 12. a, One of the secondary cells ; its nucleus a mass of young cells, b, A secondary cell elon- 

 gated into a cylinder, each cell of its composite nucleus elongated into a spiral, c, The spiral cells, 

 or spermatozoa, free. 



Fig. 13. A bunch of acini, in various states of development, maturity, and atrophy. 



The four following Figures are diagrams, arranged so as to illustrate the intimate nature of 

 the changes which occur in vesicular glands when in a state of functional activity. 



Fig. 14. A portion of gland duct with two acini. One of the acini is a simple primary cell : the other is 



in a state of development, its nucleus producing young cells. 

 Fig. 15. Both acini are advancing: the second has almost reached maturity. 

 Fig. 16. The second acinus is ready to pour out its contents, the first to take its place. 

 Fig. 17. The second acinus is in a state of atrophy, the first is ripe. 

 Fig. 18. Two follicles from the liver of Carcinus mcenas. The colourless germinal spot is at the blind 



extremity of the follicle. The secreting cells become distended with bile and oil, as they recede 



from the germinal spot. 



