EGG-LAYING IN AMPHITRITE. 26 1 



nephridial sacs, it was necessary to cut the series of oblique 

 muscles which extend from the body wall above the notopodial 

 cirrus across the cavity to the body wall in the mid-ventral 

 region. This species has five pairs of nephridia that function 

 as oviducts. The ccelomic fluid of a ripe female contains some 

 ripe eggs, many unripe ones, and thousands of corpuscles, mostly 

 red blood cells. Each nephridium to be observed was removed 

 entire and placed at once in the watch glass with the ccelomic 

 fluid. Then the watch glass was placed on the stage of a micro- 

 scope and the process studied. 



As mentioned before the fimbriated membrane is a folded, or 

 grooved structure covered for the most part with strongly de- 

 veloped cilia. The stroke of the cilia varies in direction and force 

 on different J^arts of the membrane and their action furnishes 

 the motor power that separates the eggs. By using a needle 

 I could push near the fimbriated membrane any of the bodies 

 I wished to study. The cilia are in continuous action, and their 

 effective stroke, so far as I could observe, has a constant general 

 direction. But the direction of the stroke varies on different 

 portions of the membrane as follows: (i) On the edge of the 

 membrane (Fig. 2, a) and near the entrance to the grooves 

 between the folds, the stroke is such as to send currents toward 

 or into the grooves. (2) In the grooves (Fig. 2, 6), where the 

 folds approach somewhat nearer to each other, the stroke at 

 the bottom of the groove is still onward and inward ; well up on 

 the sides of the grooves the currents move upward and outward, 

 and apparently with more force than at the bottom of the groove. 

 (3) In the main groove (Fig. 2, c] the cilia at the bottom are 

 arranged in approximately parallel lines that resemble small 

 grooves, all leading inward and their action comparatively slow. 

 Above on the sides of the pillars (Fig. 2, d), especially in the 

 narrow grooves between pillars, the currents move rapidly and 

 are directed upward and outward. With this explanation of 

 the ciliary currents, both in regard to position and action, we 

 may now consider how the different bodies are separated. 



The Separation of Blood Cells from Eggs. This occurs under 

 the conditions of my experiment principally on the outer edges 

 of the membrane. The currents are strong enough to lift and 



