174 THE EVOLUTION OF MAN. 



into the fruitful soil of the female egg-cell in order that the 

 preformed human body might unfold and grow in all its 

 parts. This radically erroneous view is now completely 

 refuted, and the most accurate researches have shown that 

 these active small seminal bodies are genuine cells, of the 

 form called flagellate. In the earlier expositions of the 

 subject a head, trunk, and tail were distinguished in each 

 of these " seminal animalcules." The so-called " head " 

 (Fig. 17 /l) is only the longish round or oval cell-nucleus ; 

 the body, the central portion («i), is only an aggregation 

 of cell material, a prolongation of which forms the tail (s). 

 We now also know that the form of these seminal animal- 

 cules is not even peculiar and unrepresented in other cells ; 

 for entirely similar vibratory cells occur in various other 

 parts of the animal body. When these cells are possessed 

 of many processes they are called ciliate cells ; but if they 

 have only one process, they are said to be flagellate. The 

 ciliated sponge particles afford instances of flagellate cells 

 resembling those of the sperm-cells. 



Thus the process of fertilization in sexual generation 

 depends essentially on the fact that two dissimilar cells 

 meet and blend. In former times the strangest views pre- 

 vailed with regard to this act. Men have alwaj^s been J 

 disposed to regard it as thoroughly mystical, and the most 

 widely different hypotheses have been framed to account 

 for it. It is only within the last few years tliat closer 

 study has shown that the whole process of fertilization i.s 

 extremely simple, and entirely without any special mystery. 

 Essentially it consists merel}'^ in the fact that the male 

 sperm-cell coalesces with the female egg-cell. Owing to its 

 sinuous movements, the very mobile sperm-cell finds its way 



