MATURATION OF GAMETES 



143 



and deutoplasmic substance is deposited in the cytoplasm (fig. 68F-H). As 

 differentiation of the oocyte advances, the enlarged nucleus or germinal 

 vesicle assumes a polar position in the egg (figs. 68H, 70F). When the oocyte 

 has finished its growth and approaches the end of its differentiation, the 



ACROSOME 



NUCLEUS 



POST ER lOR 



NUCLEAR 



PLATE 



CENTRIOLE 

 CENTRIOLE 



AXIAL 

 FILAMENT 



PROXIMAL 

 CENTRIOLE 



DISTAL 

 CE N T Rl OLE 



Fig. 78 



Fig. 79 



Fig. 78. Different shapes and positions of the acrosome. (A) Type of acrosome 

 found in Mollusca, Echinodermata, and Annelida. (B) Reptilia, Aves, and Amphibia. 

 (C) Lepidoptera. (D) Mammalia. (E) Many Hemiptera and Coleoptera. (After 

 Bowen, Anat. Rec, 28.) (F) Sperm of certain birds, i.e., finches. (After Retzius, Biol. 

 Untersuchungen, New Series 17, Stockholm, Jena.) Observe the well-developed acrosome 

 in the form of a perforatorium. The spiral twist of the acrosome shown in this drawing 

 is characteristic of passerine birds. 



Fig. 79. Sperm of urodele amphibia. (After Meves, 1897, Arch. f. mikr. Anat. u. 

 Entwichlingsgesch., 50; McGregor, 1899, J. Morphol., 15. (A-E) Stages in the morpho- 

 genesis of the sperm of Salamandra. (F) Diagram of head, middle piece, etc. of the 

 sperm of the urodele. 



