THE SIRE. 97 



regular times, varying in different animals, this descends 

 into the uterus^ for the purpose of fructification, on re- 

 ceiving the stimulus and addition of the sperm-cell of 

 the semen. 



" 4. The semen consists of two portions, — the sperma- 

 tozoa^ which have an automatic power of moving from 

 place to place, by which quality it is believed that the 

 semen is carried to the ovum ; and the sperm-cells^ 

 which are intended to co-operat6 with the germ-cell of 

 the ovum in forming the embryo. 



*'5. The ovum consists of the germ-cell — intended to 

 form part of the embryo — and of the yolk^ which 

 nourishes both until the vessels of the mother take 

 upon themselves the task ; or, in oviparous animals, till 

 hatching takes place, and external food is to be obtained. 

 The ovum is carried down by the contractile power of 

 the Fallopian tubes from the ovary to the uterus ; and 

 hence it does not require automatic particles like the 

 semen. 



'' 6. The embryo, or young animal, is the result of the 

 contact of the semen with the oviimj immediately after 

 which the sperm-cell of the former is absorbed into the 

 germ-cell of the latter. Upon this a tendency to in- 

 crease or ' grow ' is established and supported at first 

 by the nutriment contained in the yolk of the ovum, 

 until the embryo has attached itself to the walls of the 

 uterus, from which it afterwards absorbs its nourishment 

 by the intervention of the placenta. 



"7. As THE MALE AND FEMALE cacli fumisli their 



