SOME POINTS IN DEVELOPMENT OF SCORPIO FULVIPES. 589 



nuclei at various levels^ giving at first sight the appearance of 

 a folding of the walls. The outer portion (fig. 3^ iJ.) is com- 

 posed of a closely packed mass of small cells of which only the 

 nuclei can be made out. Outside this outer portion is the con- 

 tinuation of the outer layer of the ovarian tube {o.L), which con- 

 sists of flattened cells. 



In the collar (fig. 4) the two portions of the inner layer are 

 no longer distinguishable. The whole layer, which is enor- 

 mously thickened, consists of clear, highly refracting cells with 

 oval nuclei and well-marked outlines. As development pro- 

 ceeds the collar gradually moves down towards the ovarian 

 tube, and as it passes the cells of the diverticulum change 

 their form and come to resemble those of the collar. This 

 change is preparatory to the active excretion of nutritious 

 matter for the nourishment of the embryo in its earlier stages. 

 The greater thickness of the collar is simply the sign of the 

 activity of the cells within, which require more space in which 

 to undergo their change in form. When this change is 

 accomplished the diverticulum returns to its former dimen- 

 sions. 



The conical portion above the collar (fig. 1, ov) consists of 

 the egg, which when ripe is less than "2 mm. in length (that 

 of Euscorpius measuring 1"5 mm,), and of the inner layer 

 cells surrounding it. This follicle is several cells thick, the 

 cells being the same in appearance as those already described 

 in the collar. Between the egg and the lumen of the diverti- 

 culum is a small passage, the cells surrounding which are long, 

 and have their nuclei at their outer ends. These three 

 proximal portions of the diverticulum together reach a length 

 of about 2"5 mm. 



The coiled appendix, which is longer than all the rest of 

 the diverticulum, consists of a solid rod of cells (fig. 5, i.l.) 

 forming a continuation of the inner layer, and is surrounded 

 by the flattened cells which represent the outer layer of the 

 ovarian tube (o.l.). The appendix plays an important part in 

 the nutrition of the embryo, being gradually absorbed as 

 development proceeds. 



