STUDIES ON THE RELATION BETWEEN AMITOSIS 

 AND MITOSIS. 



III. Maturation, Fertilizaton, and Cleavage in Moniezia. 



C. M. CHILD. 



Since the present paper is concerned primarily with the role 

 played by amitosis and mitosis, respectively in the later history 

 of the ovum and the early development of Moniezia, the stages 

 of egg-maturation and fertilization are in themselves of secondary 

 importance. It has seemed advisable, however, to include an ac- 

 count of these stages, although it has not been possible to attain 

 certainty on a number of points, e. g., the polarity of the egg 

 before maturation, the direction of division of the chromosomes 

 in maturation, the origin of the cleavage centrosomes, etc. Fail- 

 ure to reach definite conclusions upon these points is due, at 

 least in large measure, as will appear, to the character of the 

 material rather than to insufficient observation. Much time and 

 labor has been expended in the attempt to obtain positive data 

 upon these points but thus far without success. 



The cleavage of the egg is considered from a cytological rather 

 than a morphological standpoint, and much that is of importance 

 embryologically is not discussed, as aside from the present pur- 

 pose. All the figures of maturation, fertilization, and almost all 

 of those of cleavage-stages are from Moniezia expansa but no 

 essential differences have been discovered in the two species. 

 The magnification is the same as that used in preceding papers 

 of the series. 1 



I. Maturation of the Egg. 

 In point of time the entrance of the spermatozoon precedes the 

 process of maturation and the growth of the male pronucleus 

 occurs during the formation of the polar bodies. For the sake 



1 Child, C. M., "Studies on the Relation between Amitosis and Mitosis. I., 

 Development of the Ovaries and Oogenesis in Moniezia." Biol. Bull., Vol. XII., 

 No. 2, 1907. II., Development of the Testes and Spermatogenesis in Moniezia. 

 Biol Bull., Vol. XII., Nos. 3 and 4, 1907. 



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