H 



FERTILIZATION 



(a) 



id) 



(e) 



(f) 



FIG. 4. — Entry of spermatozoon into the egg of Spirocodun saltatrix, after J. C. 

 Dan (19506). o. Unfertilized egg showing female nucleus at periphery of 

 egg and depression in egg surface; b, 30 sec. after fertilization (/.); r, 3 min. 

 35 sec. after/. Development of 'fertilization tube'; d, 7 min. 15 sec. after/. 

 Swelling and incipient disintegration of fertilization tube; e, 1 1 min. 20 sec. 

 after/. Further disintegration of fertilization tube and only tip of sperm tail 

 visible outside egg;/, 15 min. 20 sec. after/. Spermatozoon completely en- 

 gulfed, fertilization tube disintegrated and swollen fusion nucleus moving 

 away froin the periphery towards centre of egg. 



egg (Hagstrom & Hagstrom, 1954c; Hagstrom & Allen, 1956). 

 We shall examine this idea more closely in a later chapter, speci- 

 fically concerned with polyspermy. 



Movements of the male and female pronuclei. After passing 

 through the cortex, the head of the spermatozoon rotates through 



