v GENEEATIVE SYSTEM OF THE FEMALE 199 



special substances which serve to protect it against pathogenic 

 microbes, and against the toxins which they produce, agglutinating 

 the first and neutralising the second by means of antitoxins. 



VII. We have said that the ovum and the spermatozoon by 

 the union of their two pronuclei form the germ of development of 

 a new organism. Now it is noted that the organism so generated 

 reproduces the characters, both physical and psychical, of the 

 parents, not only the more generic characters, but also those more 

 peculiar to the species, and even to the individuals who have 

 co-operated in reproduction. This common and every-day obser- 

 vation compels us to admit that the germ which results from the 

 union of the sexual cells, contains in itself all the conditions 

 and characteristics necessary for the building up of the final 

 product of its development. These conditions and characters are 

 latent in the germ, that is, in a state of simple tendencies, and 

 reveal themselves to our senses progressively during development. 

 Since it is impossible to imagine these tendencies without admitting 

 that they have in the fecundated ovum a somatic substratum, it 

 follows that the organism evolved must be in some manner 

 preformed, that is, contained potentially in the complex of the 

 tendencies and their substrata. Nageli wrote in reference to 

 this : " The fertilised ova contain all the essential characters of 

 the completely evolved organism ; they do not differ less, one 

 from another, than do the adult organisms themselves. In the 

 egg of the fowl, the species is contained as completely as in tho 

 fowl itself, and the egg of the fowl is not less different from the 

 ovum of the frog than the fowl differs from the frog." 



In order to account in some way for the undeniable relation 

 between the germ and the evolved organism, between the invisible 

 characters and those which become manifest during development, 

 there were propounded in the past two principal theories, on the 

 criticism of which is based the modern doctrines of generation and 

 heredity, certainly the most difficult, loftiest, and most important 

 problems of physiology. The most celebrated and gifted naturalists 

 and physiologists of the seventeenth and eighteenth centuries, 

 Swammerdam, Malpighi, Leuwenhock, Haller, Bonnet, and 

 Spallanzani, maintained the theory of evolution which to-day one 

 is accustomed to call by the clearer and more appropriate name 

 theory of preformation. They held that the germs were from the 

 beginning identical in their structure with the adult organism, 

 that is, they contained in minute dimensions and hence invisible 

 all the organs of the adult, and in the same special relations in which 

 they are found in adults. As from the bud unfolds the flower, 

 as from the chrysalis is developed the butterfly, so from the 

 fecundated human ovum develops the adult man ; the ovum is 

 the homunculus, it is man in miniature, which contains all the 

 characters somatic and psychic which expand and display them- 



