CHAP. II. ON RUDIMENTARY TYPES. 45 



than a positive character, and altogether fails of that 

 accuracy, to be desired. Besides, it is quite evident, 

 that, if the several threads of affinity collected together 

 in the above-mentioned groups had been followed 

 up, each would have been found leading to totally dif- 

 ferent divisions of the animal kingdom. The Acrita, 

 in fact, as at present constructed, is such an ill-defined 

 group, that some writers think they are bound to bring 

 within its limits the Medusas, and many of the most 

 perfect radiated animals ; so that, if this is allowable, 

 there is no reason whatever for excluding the annulose 

 Vermes, the cephalopodous Foraminata, and the mol- 

 luscous Parenchymata. It may be thought somewhat 

 premature to state these objections, seeing that we have 

 not yet attempted to substitute any other arrangement 

 of the Acrita * for that which we hold to be a false one, 

 although proposed by the very founder of the class. But 

 we are all aware that the perception of an error, and 

 the power of rectifying it, are not inseparable. Our 

 researches may have proceeded quite far enough to 

 satisfy us on the former, and yet may not have extended, 

 or have been sufficiently matured, to accomplish the 

 latter. It is precisely in this predicament that we now 

 stand. Our researches in the true Acrita, the Radiata, 

 and the Annulosa, have advanced sufficiently far to 

 convince us of the fundamental truth of what we have 

 just advanced. The subject, however, is of such vast 

 importance to the first principles of natural arrange- 

 ment, that we may well devote to it a few additional 

 remarks. 



(37.) If we look to the vertebrated circle of animals, 

 we find that many of the amphibians are the most 

 simply constructed of all the Vertebrata ; the Amphiuma 

 are worm-like salamanders, having the body excessively 



* We trust this investigation may be taken up by the only naturalist 

 of this country who has devoted himself to the study of the sort Mollusca t 

 and from whose talents, experience, and zeal, we may expect so much 

 Dr. Johnson. It is a serious loss and inconvenience to science, that the 

 numerous and truly valuable memoirs of this accomplished malacologist 

 are now scattered in periodicals and magazines, almost hid in a mass of 

 temporary and trivial articles. 



