THE OVARIAN EGG. 281 
eggs, or produced by natural division, or by 
budding ; and that the constancy of these normal 
processes of reproduction, as well as the uni- 
formity of their restlts, precludes the idea that 
the specific differences among animals have been 
produced by the very means that secure their 
permanence of type. The statement itself im- 
plies a contradiction, for it assumes that the same 
influences prevent and produce changes in the 
condition of the Animal Kingdom. Facts are all 
against such an assumption; there is not a fact 
known to science tending to show that any being, 
in the natural process of reproduction and multi- 
plication, has ever diverged from the course nat- 
ural to its kind, or that a single kind has ever 
been transformed into any other. But this once 
established, and setting aside the idea that Em- 
bryology is to explain to us the origin as well 
as the maintenance of life, it yet has most im- 
portant lessons for us, and the field it covers 
is constantly enlarging as the study is pursued. 
The first and most important result of the 
science of Embryology was one for which the 
scientific world was wholly. unprepared. Down 
to our own century, nothing could have been 
farther from the conception of anatomists and 
physiologists than the fact, now generally admit- 
ted, that all animals, without exception, arise 
from eggs. Though Linnzus had already ex- 
