32 CLASSIFICATION 



globules enveloped in a common membrane without any 

 opening. Then this form varies by tapering' at one ex- 

 tremity into a kind of tail or neck. Next we see 1 them 

 endowed with external organs, consisting of hairs or 

 bristles. Again instead of a cavity without an opening 

 as is the case in all that we have yet described, we find 

 at one extremity a distinct aperture, thus forming the 

 first rudiment of an alimentary canal. Next we meet 

 with processes or lashes around the opening for the pur- 

 pose of propelling the fluid by their motion into the ali- 

 mentary cavity. Thus we may go on tracing these 

 minute forms of organisation through their increasing 

 complexity until at last we come by these small grada- 

 tions, to beings endowed with a special digestive organ 

 and special organs of motion. 



Emily. We are to conclude then, T suppose, that 

 the elementary globules which compose the primitive 

 tissues are living bodies capable, when separated from 

 each other of spontaneous motions and that it is upon 

 this one simple organic point, that every form of organic 

 matter is built up from the Infusoria even to man him- 

 self. In truth, this is a most interesting and curious 

 fact. 



Dr. B. Such a conclusion would, no doubt be just, 

 were the accuracy of these observations beyond a ques- 

 tion. But since other naturalists have been unable to 

 verify them and hence have doubted the ac'curacy of their 

 results, we are thereby not warranted in adopting this 

 general principle. 



Having now described the primitive tissues, our next 

 step will be to consider the several organs which they 

 form, and the functions which their organs accomplish. 



Emily. If they are numerous, I never shall remem- 

 ber much about them without the aid of some classifica- 

 tion. May we not divide the body into head, trunk and 

 limbs, and these again into smaller divisions ; then we 

 should greatly facilitate the study of them. 



Dr. B. The various organs are already classed., 



