NUCLEOLAR STRUCTURES OF THE CELL. 159 



and a nietaphase, from the time of the discharge of the secre- 

 tion until the latter has been completely discharged. This 

 includes the cycle of activity of the cell, and it is probable that 

 this cycle is passed through once during each season of sexual 

 maturity of the animal. My deductions as to the sequence of 

 the stages were based upon an examination of a number of 

 individuals of various sizes. 



At the commencement of the propJiase the spherical nucleus 

 contains a single, more or less rounded nucleolus. The cell 

 body increases gradually in size, and secretion globules, which 

 stain much in the same way as the nucleoli, make their appear- 

 ance at some distance from the nucleus. The cell steadily in- 

 creases in size as do the nucleus and nucleolus, and then the 

 latter elongates and passes to the nuclear membrane. There 

 it continues to grow in volume, at the same time becoming so 

 irregular in form that in no two nuclei does it present the 

 same outlines ; 6^-shaped, 5-shaped, and all kinds of irregularly 

 lobular forms are gradually produced. Then the nucleolus 

 commences to break up into pieces, and these fragment further, 

 until finally several hundred minute nucleoli are scattered 

 through the nucleus, in the place of the original large one. 

 During this time the cell body has become greatly dilated, 

 owing to the formation of secretion globules which are now 

 crowded throughout the cytoplasm. Simultaneously the nucleus 

 has increased in volume, and to a greater relative extent than 

 the cell body ; and it has gradually become excessively amoe- 

 boid in form, sending out long, branching, and anastomosing 

 processes, on which a nuclear membrane does not appear to 

 be present. These nuclear processes extend nearly to the 

 proximal end of the cell duct, and so penetrate between and 

 come into direct contact with the secretion globules. 



The metaphase of the gland cell commences with the dis- 

 charge of the secretion corpuscles ; and here it may be noted 

 that the secretion appears to have been formed in the cyto- 

 plasm of the duct as well as of the cell body. During the 

 process of discharge the duct becomes swollen. After a con- 

 siderable portion of the secretion has been extruded, approxi- 

 mately a third of that previously present in the cell body, the 



