176 THE MAMMALIAN EGG 



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to the method of transfer.' Sci. Bull. Fac. Agric, Kyushu Univ. 16, 171. [139] 



Zeuthen, E. (1951) 'Segmentation, nuclear growth and cytoplasmic storage in eggs of 

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Zotin, A. I. (1958) 'The mechanism of hardening of the salmonid egg membrane after 

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Zuckerman, S. (1960) 'Origin and development of oocytes in foetal and mature mammals.' 

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ADDENDUM 



The important observations of A. L. Colwin and L. H. Colwin, referred to on p. 88, 

 have now been published: 



Colwin, A. L., & Colwin, L. H.: 



(1961a) 'Fine structure of the spermatozoon of Hydroides hexagonus (Annelida), with special 



reference to the acrosomal region.' J. biophys. biochem. Cytol. 10, 211. 

 (1961b) 'Changes in the spermatozoon during fertilization in Hydroides hexagonus (Anne- 

 lida). II. Incorporation with the egg.' J. biophys. biochem. Cytol. 10, 255. 

 Colwin, L. H., & Colwin, A. L. (1961) 'Changes in the spermatozoon during fertilization 

 in Hydroides hexagonus (Annelida). I. Passage of the acrosomal region through the 

 vitelline membrane.' J. biophys. biochem. Cytol. 10, 231. 



