ON GENERATION. 171 



abroad, a foetus is produced; whence such animals are called 

 oviparous or vermiparous. Viviparous animals are so entitled 

 because they retain and cherish their conception in their interior, 

 until from thence the foetus comes forth into the light com- 

 pletely formed and alive. 



EXERCISE THE SECOND. 



Of the seat of generation. 



" Nature/' says Fabricius, " was first solicitous about the 

 place [where generation should proceed] , which she determined 

 should be either within or without the animal : within she or- 

 dained the uterus ; without, the ovum : in the uterus the blood 

 and seminal fluid engendering ; in the ovum, however, the fluids 

 or elements of which it consists supplying pabulum for the pro- 

 duction of the foetus/' 



Now, whatever is procreated of the semen properly so called 

 originates and is perfected either in the same place or in dif- 

 ferent places. All viviparous creatures derive their origin and 

 have their completion in the uterus itself; but oviparous animals, 

 as they have their beginning within their parents, and there be- 

 come ova, so is it beyond their parents that they are perfected 

 into the foetal state. Among oviparous animals, however, there 

 are some that retain their ova till such time as they are mature 

 and perfect ; such as all the feathered tribes, reptiles and ser- 

 pents. Others, again, extrude their semina in a state still im- 

 mature and imperfect, and it is without the body of the parent 

 that increase, maturity, and perfection, are attained. Under 

 this head we range frogs, many kinds of fishes, crustaceous, 

 molluscous, and testaceous animals, the ova of which, when first 

 extruded, are but beginnings, sketches, yelks which afterwards 

 surround themselves with whites, and attracting, concocting, 

 and attaching nutriment to themselves, are changed into perfect 

 seeds or eggs. Such also are the semina of insects (called worms 

 by Aristotle), which, imperfect on their extrusion and in the 

 beginning, seek food for themselves, upon which they are nou- 

 rished, and grow from a grub into a chrysalis : from an imper- 

 fect into a perfect egg or seed. Birds, however, and the rest 

 of the oviparous tribes, lay perfect eggs ; whence without the 



