3io 



MYRA MELISSA SAMPSON. 



IV. THE POTENCY OF SPERM FILTRATES AND DIALYZATES ON 

 OVA OF THE SAME SPECIES. 



a. Arbacia punctulata. The procedure employed to determine 

 the effect of these preparations on ova of the same species and 

 the results obtained are described first for Arbacia. The ova 

 were exposed to the action of sperm filtrates and dialyzates in 

 the proportion of two milliliters of fresh washed eggs to twenty- 

 five milliliters of the test solution. Sea-water controls ac- 

 companied every experiment and samples of eggs from test 

 solution and from sea-water were examined at intervals. 



FIG. 2. Changes in shape and nuclear changes in ova exposed to sperm filtrates. 

 15 = changes in a single ovum within forty-five minutes; 613 = ova repre- 

 senting various changes produced by filtrates. Magnification X 350. 



The first evidence of the influence of the filtrate or of the 

 dialyzate on the ova is a change in the density of the cytoplasm 

 at or near the center of the ovum, similar to that which precedes 

 nuclear division in inseminated eggs. Indeed nuclear changes 

 and nuclear division follow. Simultaneously a distortion of the 

 egg occurs followed by its partial or complete cleavage into two 

 or more parts. The cleavages are at times perfectly regular, at 

 times unequal. Even the smallest cells are usually nucleated. 

 Segmentation sometimes proceeds to the eight-celled stage, but 

 in any case is followed, if the eggs remain in the filtrate, by a 



