738 GENERATION AND DEVELOPMENT. 



the right composition of the impregnating fluid, is shown 

 both by the position of the glands and by their enlarging 

 with the testicles at the approach of an animal's breeding 

 time. But that they contribute only a subordinate part is 

 shown by the fact, that, when the testicles are lost, though 

 these other organs be perfect, all procreative power ceases. 



The mingled secretions of all the organs just described, 

 form the semen or seminal fluid. Its corpuscles have been 

 already described (p. 734) : its fluid part has not been 

 satisfactorily analysed : but Henle says it contains fibrin, 

 because shortly after being discharged, flocculi form in it 

 by spontaneous coagulation, and leave the rest of it 

 thinner and more liquid, so that the filaments move in it 

 more actively. 



Nothing has shown what it is that makes this fluid with 

 its corpuscles capable of impregnating the ovum, or (what 

 is yet more remarkable) of giving to the developing off- 

 spring all the characters, in features, size, mental disposi- 

 tion, and liability to disease, which belong to the father. 

 This is a fact wholly inexplicable : and is, perhaps, only 

 exceeded in strangeness by those facts which show that 

 the seminal fluid may exert such an influence, not only on 

 the ovum which it impregnates, but, through the medium 

 of the mother, on many which are subsequently impreg- 

 nated by the seminal fluid of another male. It has been 

 often observed, for example, that a well-bred bitch, if she 

 have been once impregnated by a mongrel dog, will not 

 bear thorough-bred puppies in the next two or three 

 litters after that succeeding the copulation with the 

 mongrel. But the best instance of the kind was in the 

 case of a mare belonging to Lord Morton, who, while he 

 was in India, wished to obtain a cross-breed between the 

 horse and quagga, and caused this mare to be covered by 

 a male quagga. The foal that she next bore had distinct 

 marks of the quagga, in the shape of its head, black bars 

 on the legs and shoulders, and other characters. After 



