FERTILIZATION AFTER INITIATION OF DEVELOPMENT. 283 



TABLE IV. 



Series Preserved in Picro-acetic Acid. 



I x killed 5:30 P.M. I y 1 killed 5:30 P.M. I y" killed 5:45 P.M. 



II x " 5:50 " II y 1 " 5:35 " II y- " 5:50 " 



III x " 5:25 " III yi " 5:40 " Illy* " 5:55 " 



IV x " 6:15 " I\ T yi " 6:15 " IV y 2 



The general cytological observations on this preserved series 

 are as follows: In all lots of eggs exposed to the stronger con- 

 centration, from five minutes to fifty minutes, and inseminated 

 immediately upon their return to sea-water, sperm have pene- 

 trated the eggs freely and lie in any plane of the egg cytoplasm 

 from the periphery to the center. No attempt has been made 

 to determine by actual count, from sections, the relative pro- 

 portion of eggs containing spermatozoa, but this condition is 

 found under every field of the microscope and many sections of 

 eggs show from two to sometimes twenty sperm heads. By 

 far the larger number of eggs show the presence of sperm heads 

 imbedded within the cytoplasm. 



The effects of the egg cytoplasm environment upon the in- 

 dividual spermatozoon varies in the different eggs in which they 

 are found. Many sections prove by their presence that three, 

 four or more spermatozoa have entered the egg and react with it, 

 thus giving the picture of a typical case of polyspermy ; the sperm 

 heads may be separated from the egg nucleus and accompanied 

 by a sperm aster, or two or three may have copulated with the 

 egg nucleus. In other sections a dozen spermatozoa -may be 

 scattered throughout the cytoplasm, but thirty minutes after 

 insemination they exhibit not the slightest perceptible change 

 in size or shape (see Fig. 2).- They appear perfectly solid with 

 no indications of vacuolization ; there is no indication of a sperm 

 aster, and in short the sperm heads appear only as inert foreign 



