432 ANATOMICAL AND PATHOLOGICAL OBSEBVATIONS. 



as might have been expected, had the secondary cells been 

 formed from it. After these primary cells have burst, the 

 secondary cells contained in them pass down the seminal tube, 

 to undergo the changes to be afterwards described. 



The spindle-shaped cells in the lower part of the seminal 

 tube are large primary cells, two or three generally arising 

 from a disc or spot in the germinal membrane. They corre- 

 spond in every respect, except in shape and size, to the 

 spherical primary cells further up the tube, and like them 

 form in their interior young or secondary cells. These 

 secondary cells originate in a germinal spot or nucleus, situated 

 about a third from the attached extremity of the cell. In 

 such of the spindle-shaped cells as are quite full of secondary 

 cells, this nucleus cannot be seen, so that it probably dis- 

 appears after the primary cells have become fully developed — 

 that is, have become full of young. In such of these elongated 

 cells, again, as are not quite developed, with cavities not en- 

 tirely occupied by their progeny, the nucleus may be occasion- 

 ally seen in various stages of development, with a brood of 

 young cells surrounding it, and enclosed in a membrane carried 

 off by them from the nucleus (Fagurus). 



These spindle-shaped primary cells of the lower part of 

 the seminal duct differ from the spherical primary cells of the 

 upper part of the same tube, princi^^ally in this, that whereas 

 the latter contain only a limited number of secondary cells, 

 formed probably by a single act of nuclear development, the 

 former are filled by successive broods from the nucleus. 



In Hyas, when these spindle-shaped cells project from the 

 external surface of the seminal duct, instead of into its cavity, 

 the secondary cells pass off by a narrow A'alvular orifice in its 

 attached extremity, and are replaced by others from the 

 nucleus. The cell in this case has become a secreting follicle, 

 with an active germinal spot. 



The passage downwards of the secondary cells, both of the 



