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les. différences trés rélatives qui existent entre ces organes micro= 
scopiques. Tout en professant le plus grand respect pour les tra- 
vaux des savants qui suivent cette voie, nous estimons qu'il n'est 
pas rationnel de fonder sur des organes caducs la classification 
d'animaux dont la plus grande partie est fossile”. The same opinion 
is also expressed by Lambert in M. Boule and A. Thevenin: 
Fossiles de la cåte orientale de Madagascar (Annales de Paléonto- 
logie I, 1906, p. 56). "Sans nier la valeur des caractéres fournis 
par les organes caducs et microscopiques de 1'Échinide, j'estime que 
leur momenclature doit surtout étre fondée sur un ensemble de 
caractéres observables, aussi bien chez les fossiles que chez les 
vivants”. 
This is evidently quite å new principle introduced into classi- 
fication, that only structures which are liable to be preserved in 
fossils must be taken into consideration for systematic characters. 
Let us look a moment on the results which would follow from au 
application of this principle, taking as granted that Echinoids 
cannot be classed in a totally different way from all the 
rest of the animal kingdom. The first result appårently is that 
the whole animal kingdom must be divided into two main divisions, 
viz. those which are found fossil and those which are not, the 
latter division apparently being incapable of elassification, since none 
of their structures are preserved by fossilization. Thus for instance 
a very large part of the Protozoa (Infusoria, Amæba, etc.), the 
Tunicata and most of the worms. are lost for classification, while 
others, like the Vertebrata, Arthropods, Mollusca, Echinoderms and 
Corals are still fairly well off. Some remain very doubtful, e. g., 
the: Medusæ, For the rest of the animal kingdom, viz. those forms 
which are fortunate enough to possess structures which may be 
preserved by fossilization, the number of the characters avail- 
able for classification is considerably restricted. The internal ana- 
tomy in general must: be left out of consideration. The placenta 
in mammals; is that ever preserved in fossil specimens? Or the 
arrangement of the feathers in birds, not to speak of their color! 
