578 GENERATION AND DEVELOPMENT. 



neous 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 offspring all the 

 characters, in features, size, mental disposition, and liability 

 to disease, which belong to the father. This is a fact wholly in- 

 explicable ; 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 sub- 

 sequently impregnated 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 belong- 

 ing 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 char- 

 acters. After this time she was thrice covered by horses, and 

 every time the foal she bore had still distinct, though decreas- 

 ing marks of the quagga ; the peculiar characters of the quagga 

 being thus impressed not only on the ovum then impregnated, 

 but on the three following ova impregnated by horses. It 

 would appear, therefore, that the constitution of an impreg- 

 nated female may become so altered and tainted with the 

 peculiarities of the impregnating male, through the medium 

 of the foetus, that she necessarily imparts such peculiarities to 

 any offspring she may subsequently bear by other males. Of 

 the direct means by which a peculiarity of structure on the 

 part of a male is thus transmitted, nothing whatever is known. 



DEVELOPMENT. 



Changes in the Ovum previous to the Formation of the Embryo. 



Of the changes which the ovum undergoes previous to the 

 formation of the embryo, some occur while it is still in the 

 ovary, and are apparently independent of impregnation : 

 others take place after it has reached the Fallopian tube. The 

 knowledge we possess of these changes is derived almost ex- 

 clusively from observations on the ova of mammiferous ani- 



