a particular order, class, and family. lam 
r from believing in the identity of germs. But there is a resem- 
blanee, and this resemblance is salve: as we approach the period of 
their origin. Hence it is that the embryogenic history of animals il- 
lustrates s so fully and beautifully their natural relations.” 
In carrying out these principles it becomes evident that there is a 
natural system in animal nature, based upon a single grand principle; 
and farther that this system cannot be re nted imple lineal 
4 00) en: * re a multitude of series which n e conceived 
of as branching from one another at different : heights, or rather which 
are reunited at base, and separate and subdivide into secondary, ternary, 
quarternary groups, according as they diverge and take their distinctive 
haracters, more or less near the origin of their embryonic existence.” 
n 
organogenic, or 
the organs producing eapealepicn! phenomena ; and 
ic, he modific ations arising m the various combinations 
ers; and different results arise from their unequal develop- 
“hus, two series of histogenic phenomena of the same kind, in 
ent animals, or two series of such phenomena of different kinds 
; but ata period more or less advanced, these terms will 
os analogous, and in Eonar the divergence will continue to 
e as they approach the final result.” In this manner, by an 
z of Leunlogaaaah of different tissues or organs, at different pe 
nimal becomes widely different rie: -another, and there will be 
ogy between a finished tissue of what we designate an inion 
r 7 
the apparsenad ne these principles, we th the concordance be- 
en th 
of the embryo ts: end r species whose tert career is lo nger 
Continued.” In a natural group, the — with a short period of de- 
velopment, start upon the same route which those have followed that 
have left them on the oad. Thea sina therefor, whose em embryog' 
uces igher 
grade. But il are instances of a degradation from the same source, 
as with the Lernzas, which, in a transitory state, have a rank eoneee- 
ponding with the Cai though afterwards so inferior in character 
Milne Edwards uses the term direct affinity _ the immediate relations of spe- 
cies ; > collateral affinity, for the relations of paralle | series. 
