20 HISTORY OF THE EGG FROM FERTILIZATION TO CLEAVAGE. 



preparation is the micropyle, as this is more easily recognized than the 

 nuclear bodies. With the position of the micropyle determined, the field 

 in which to look for the polar spindle and spermatic body is comparatively 

 small, and a little experience enables one to find them readily. 



For sections, it is well to select preparations in which the parts are 

 oi'iented, as in Fig. 6, and then imbed in such a position that everything 

 of importance may tall in the plane of a single vertical section. It is 

 much more difficult to recognize the spindle and the spermatic body in 

 sections than in surface views, and hence the necessity of so orienting the 

 imbedded object that one will know precisely where to search for any 

 given part. After taking all these precautions, the identification of parts 

 is not always easy. The spermatic body has given us the most trouble, 

 and we have not succeeded in setting anv views in sections that would 

 explain its appearance in Figs. 2, 3, 4, 6, and 7. 



b. Observations. — a. The Spermatic Bod//. Position of Mycropyle } etc. — 

 In surface views of the germinal pole immediately after fertilization, Figs. 

 1-7, Plate XXII., the micropyle and polar spindle stand at distances varying 

 from 40 n to 140 /x. Most preparations show a peculiar body lying in the 

 neighborhood of the micropyle, usually nearer than the spindle, but some- 

 times more remote, as in Fig. 6. The constancy of this body makes it 

 certain that it is not an artificial product ; but its position with relation to 

 the micropyle renders it a little doubtful whether it is spermatic. As the 

 egg is in close contact with the membrane, or very nearly so, at this time, 

 one would expect to find the spermatozoon just beneath the micropyle. 

 Allowing that there is a thin space between the egg and its membrane, 

 the possibility of movement inside the membrane becomes evident, not 

 only for the egg, but also for the spermatozoon. It certainly seems prob- 

 able from what we know in other eggs, that the first polar spindle has a 

 constant position. Assuming this, it follows that the position of the micro- 

 p}de must vary within certain limits, or that it has moved from its normal 

 position in most preparations. It will be seen from Figs. 1-7 that the 

 spermatic (?) body shows no constant relation either to the micropyle or 

 to the spindle, and this fact certainly suggests that the spermatozoon may 

 move about inside the egg membrane before entering the egg. Such a 

 movement, however, presupposes a perivitelline space actually separating 

 the inner opening of the micropyle from the egg sphere at the time the 

 spermatozoon passes the micropyle. The weight of authority is against 



