THE MALE-CELL OR SPERMATOZOON, 



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of which the subject is now emerging. In a general way, 

 the process is simply that of the varied segmentation of a 

 mother-sperm-cell, and the occurrence of a series of preparatory 

 stages before the sperm is finally matured. In detail, however, 

 there are many variations, and these are described in a maze of 

 often tautologous and ambiguous terms, such as spermatogonium, 

 spermatoblast, spermatospore, spermatogemma, spermatomere, 

 spermosphere, and a dozen more. 



One of the most defensible set of terms is that used by Voigt after 

 Semper, and also by Von la Valette St George, who has worked per- 

 sistently at the subject for over twenty years. The sperm or spermatozoon 

 is differentiated from an immature cell or spermatide, this is modified from 

 or descended from a spermatocyte, the spermatocytes result from the 

 division of the mother-sperm-cell or spermatogonium, and this finally is a 

 modified form or a descendant of the primitive sex-cell or male ovule. 



Cuniparison of Spermatogenesis and Ovum Segmentation. 



Explanation. — The first line, A-E, exhibits types of ovum segmentation : — A, regular morula ; 

 B, unequal segmentation, e.g:, in some Molluscs ; C, centrolecithal or peripheral type, e.^., 

 in a shrimp Peneus ; D, partial segmentation; E, the same, with the cells less markedlj" 

 defined off from the yolk. 



In the next two lines various types of spermatogenesis are collated with the above to 

 illustrate the parallelism : — A' and A", morula type, as in Sponge, Turbellarian Spider, &c. ; 

 B' and B", where the division is unequal, and one large nutritive cell is seen (Plagiostome 

 fishes, Von la Valette St George); C and C", after Blomfield, Jensen, &:c., showing 

 central cytophoral or blastophoral nutritive portion ; D' and D", sperm-blastoderm, with a 

 few formative cells on large nutritive blastophore, after Gilson, 8zc. ; E' and E ', the fame, 

 with the sperm cells less definitely separated off, after Von Ebner and his followers. 



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