ON THE ART OF CLASSIFYING. 35 
are not radiant, but are placed in this type on account of the 
imperfection of their organisation alone. 
It is to Von Barr especially that we are indebted for a clear 
insight into this distinction’. He considers the classes as sub- 
divisions of the fundamental form or type, which differ in respect of 
the higher or lower grade of organisation. We may conceive the 
matter differently, thus: that every animal class is determined by 
two factors, of which one is the type of organisation, the other the 
perfectness of structure. The highest perfectness is in general 
linked to the type of the vertebrates: yet how imperfect, how poor 
(if I may use the term) the organisation may be, even in a verte- 
brate animal, the anatomical investigation of amphioxus lanceolatus 
in recent times has taught us. That this little fish is in complexity 
of organisation far surpassed by many insects and molluscs, cannot, 
on unprejudiced examination, be denied. 
In the arrangement, therefore, of classes, we shall lay down as 
our basis this idea of type of organisation, and shall thus avoid 
separating that which is connected by natural transitions. "We 
begin with the Radiata, because in this type organisation stands on 
the lowest grade, and even the most perfectly organised radiates 
are surpassed by a great, nay the greatest, number of Annulates 
and Molluscs in complexity of organisation, variety of functions, 
and multifarious enjoyment of life. Whether, after these, we pro- 
ceed with the Annulata or the Mollusca, is in a certain sense indif- 
ferent. Nature has not formed the creatures in a single ascending 
rank. Were this the case, then would a single type necessarily 
prevail in them all: yet even in the divisions (classes, orders and 
families) belonging to a single type, we are not able to discover 
such a simple ascent of organisation. The most perfect fish-is not, 
by proximate affinity, jomed on to the least perfect of the reptiles: 
nor the most composite bird to the most imperfect mammal. It 
was a pleasing dream of the amiable BonNer?, that all creatures 
1 Bettrdge zur Kentniss der niedern Thiere, von Dr. K. A. v. BAER, Nov. Act. Cas. 
L. C. Nat. Curios. Vol. xi. P. 11. 1827. s. 523—762, especially s. 739—759; Ueber 
Entwickelungsgeschichte der Thiere. Beobachtung und Reflexion. 49.1. Konigsberg, 1828. 
s. 207—219. In France also similar ideas were afterwards advanced by MILNE 
Epwarbs. See ex. gr. his remarks in the new edition of Lamarck: Histoire Nat. des 
Ani. s. vert. 1. Paris, 1835, pp. 335—337, revised by him and DEsHAYEs. 
2 Contemplation de la Nature. (Euvres d’ Hist. Naturelle et de Philosophie de Cu. 
Bonnet. Tome vit. Neufchatel, 1781, Svo. pp. 51—55, and other places. 
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