418 PALEONTOLOGY OF ILLINOIS. 



restitutions, that the expanding and incrusting forms may gradually assume 

 the ramose or convolute modes of growth. On reflection, it will be readily 

 perceived how these accidental modifications of form may be developed, for the 

 approximating borders of an expansion may fail to meet each other in exact 

 apposition, and the convolute form be induced, or an excess of development at 

 certain points on the surface or the margin of the polyzoum may give rise to 

 the ramose forms; or if this latter should be arrested, to a simple tuberculation 

 of the surface. 



It will be readily inferred, from these observations, how much difficulty at- 

 tends the correct classification of this order of the animal kingdom, in which 

 the generic and specific characters are so extremely limited. If we leave out 

 of consideration external forms, which are so invariable and definite in the 

 higher orders of animal life, and search into the minute anatomical elements 

 of their organization, we scarcely feel more secure in our distinctive determi- 

 nations; for when these are profoundly investigated and viewed in all their 

 relations, they seem but modifications, gradually taking their origin in a com- 

 mon type, as with the Anthozoa, modified as it is into all the beautiful and 

 diversified forms which it presents. We are enabled to ground our groupings 

 into families and genera only on developments, when not accidental, which re- 

 sult from the plastic calcareous or corneous secretions and the form and general 

 arrangement of the cells or chalices; while for specific distinctions we are 

 restricted to narrower limits, or to details of minor importance, such as the 

 relative size and form of the cells, their number and distance apart, and some- 

 times to phenomena of a purely negative character. 



These principles, when more accurately defined, and limited to their proper 

 sphere, may lead to a more correct classification or a more natural arrangement 

 of the Polyzoa than those which have been previously proposed. It must be 

 admitted that the present classification is almost as defective in Polyzoology 

 as when the profound and gifted mind of deOrbigny essayed to establish order 

 where the wildest confusion had previously prevailed. In all deference to his 

 genius and his labors, which are worthy of all praise, we are compelled to be- 

 lieve that he has given too great an expansion to many parts of his system by 

 the multiplication of genera in the different groups, and has sometimes associa- 

 ted forms which have no generic affinities, from losing sight of the terms or the 

 characters on which his distinctions were founded. Those who fully compre- 

 hend the difficulties of a correct classification of these often minutely developed 

 forms of living beings, will regard with proper indulgence these errors in an 

 attempt to restore order where nothing but the most indiscriminate complexity 

 had formerly existed. In attempting to make our descriptions conform to a 

 strictly natural system, we are not certain that we shall meet with greater suc- 

 cess. All that we can promise is to adhere strictly to this basis of classification, 



