Zoological Classification. 439 



tion to the state of the classification of these creatures, and the 

 changes recently proposed in it. 



We are not specially zoologists, but have devoted some atten- 

 tion to the subject in its relations to geology, and as interesting 

 in itself, as well as in connection with the teaching of its? elements 

 to students. We speak, therefore, as addressing zoological spe- 

 cialists from without their own circle, and desire to do so with all 

 the humility becoming this exoteric position. 



A number of zoologists have lately added to the Cuvierian 

 fourfold division of the animal kingdom, two new types of Pro- 

 tozoa and Coelenterata, the former being probably more widely 

 accepted than the latter, though it also is supported by some high 

 names. We have not been able to convince ourselves of the 

 necessity of either of these groups, in the rank assigned to them; 

 and, on the contrary, fear that their establishment will tend to 

 confuse our conceptions of the natural subdivisions of animals. 



The group of Protozoa is confessedly distinguished from the 

 others merely by negative characters, — ^by deficiency of impor- 

 tant systems of organs, as of nervous system and organs of sense. 

 It cannot, therefore, be regarded as embodying a type of structure 

 distinct from those of the Radiates, Mollusks, and Articulates^ 

 but rather as embracing all the creatures which are so simple that 

 we cannot recognise in them any distinct type. It is obvious that 

 such a group, however convenient, cannot be recognised as co- 

 ordinate with the others above named, and that it must be merely 

 provisional, containing animals whose afiinities have not yet been 

 ascertained, and which may be humbler members of one or all of 

 the other recognised types. The real question as to the position 

 of these creatures is this. — Can we ascertain their aflBnities? 

 If we can, let us place them in their true relations. If not, let us 

 admit that they do not consitute a veritable sub-kingdom, but 

 merely a residuum which we are unable to classify. 



Regarding, with Carpenter, the Protozoa as consisting of Phi- 

 zopoda, Porifera, Infusoria, and Grec/arinida,^ it is at once ap- 

 parent : (1.) That all these creatures, in point of simplicity of 

 structure, are as low as, or lower than the humblest members of 

 the other invertebrate kingdoms. (2.) That they do not present, 

 in any distinct form, the types of structure characteristic of these 

 sub-kingdoms. (3.) That many of them strongly resemble the 



* These latter may possibly be humble Entozoa. 



