CONCLUSION. 141 



A310NG the general conclusions which 

 may be deduced from the preceding obser- 

 vations, it appears that the genus is suscep- 

 tible of subordinate divisions, according to 

 peculiar organization ; though analogous 

 properties are seen where the structure is 

 different. In one extensive class, the aper- 

 ture of the mouth is remote from the head, 

 and under certain circumstances, is even 

 diametrically opposite to it. This aper- 

 ture is the extremity of an exsertile tube, 

 by which the food is conveyed into nume- 

 rous viscera, distributing it by delicate ra- 

 mifications throughout the body. Should 

 the substances which are voraciously ab- 

 sorbed, be coloured, the hue of the whole 

 planaria, except the head and a marginal 

 band of the remainder, is altered. By 

 means of an organ probably situated to- 

 wards the tail, a glutinous or silky matter 

 is prepared in threads, which are singly in- 

 visible to the naked eye, but become per- 

 ceptible when accumulated in numbers. 



