The Evolution of Man — Volume 1 by Ernst Heinrich Philipp August Haeckel
page 149 of 358 (41%)
page 149 of 358 (41%)
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and tail. The "head" (Figure 1.20 k) is merely the oval nucleus of the
cell; the body or middle-part (m) is an accumulation of cell-matter; and the tail (s) is a thread-like prolongation of the same. Moreover, we now know that these spermatozoa are not at all a peculiar form of cell; precisely similar cells are found in various other parts of the body. If they have many short threads projecting, they are called ciliated; if only one long, whip-shaped process (or, more rarely, two or four), caudate (tailed) cells. Very careful recent examination of the spermia, under a very high microscopic power (Figure 1.22 a, b), has detected some further details in the finer structure of the ciliated cell, and these are common to man and the anthropoid ape. The head (k) encloses the elliptic nucleus in a thin envelope of cytoplasm; it is a little flattened on one side, and thus looks rather pear-shaped from the front (b). In the central piece (m) we can distinguish a short neck and a longer connective piece (with central body). The tail consists of a long main section (h) and a short, very fine tail (e). The process of fertilisation by sexual conception consists, therefore, essentially in the coalescence and fusing together of two different cells. The lively spermatozoon travels towards the ovum by its serpentine movements, and bores its way into the female cell (Figure 1.23). The nuclei of both sexual cells, attracted by a certain "affinity," approach each other and melt into one. The fertilised cell is quite another thing from the unfertilised cell. For if we must regard the spermia as real cells no less than the ova, and the process of conception as a coalescence of the two, we must |
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