430 Scientific I 
ning through one group, are repeated in anot ther series. ~ 
oup, says Milne Edwards, is a reunion of all the de srivetives 
same type; a primary division includes all derived from the same pri- 
mary type, or plan of development—and a secondary division, those 
fourth, &c., orders, and groups corresponding to each. Moreover each 
group may contain several natural series, pinned or otherwise, and 
The importance of emb: as a means of distinctions, is at once 
ovum of the vertebrate animal, the first step is the formation of the 
medial depremion which divides the’ central portion of the blastoderm 
into two symmetrical halves, and corresponds to the vertebral column 
and its adjuncts. There is nothing similar in the invertebrata. Thus 
‘the very first point observed in the embryo of a bactige ani 
that which is the dominant characteristic in this whole divisic 
peculiarities are pointed out in the memoir for the dcriead 
and Radiata, which bear out the same pens 
Milne Edwards ts reasons for separating the 
the Reptiles, as first proposed by Blainville, and thus 
divisions of the ustebian —the Mammifera, Birds, 5 
chia, kd Fishes. The Reptiles are, eetaton fit, aérial in 
tion, whilst the nape ‘in their early state at leant, have bri 
, that the embryo of Fishes and A 
have no allantoid nor pha whilst in the true Reptiles, Birds an 
mifera, these parts are always distinct. He hence divides the Ve 
into the Vertébrés: Allantoidiens and the Vertébrés Anallant 
importance, we have to pass’ es ve this —— giving only in é 
form the classification which he propos 
A. VERTEBRES ALLANTOIDIENS. 
a © Mamuiréres. 
elphiens ou Mammiféres ube sages 
lammiféres a placenta discoi 
_ Bimanes, Quadrumanes, ot teaeen 
_Cheiroptéres, Rongeurs 
Pa achydermes, Solipédes, Ruminans, ae 
Siréniens, Cétacés, Edentés. 1 Bee 
Didelphiens. 
Marsupiaux. 
Insectivores, Herbivores. 
Monothrémes. 
1 Bek AEE HES Gee 
