96 PLANARIA. 



acquainted with all the phenomena of nature, and especially of animated 

 nature, as far as our limited faculties will admit, seeing we are ourselves 

 one great portion of it ; and as the farther we go, so shall the mind be 

 exalted higher. 



The stimulus thus given to inquiry, has induced the later study of 

 naturalists to rescue from oblivion many of those beings unknown to the 

 superficial, or contemned by the ignorant ; and now they prove alike in- 

 teresting as those familiar for centuries. Some of them also serve to 

 replenish the void which seemed to be interposed between the various 

 animal tribes of the earth and of the waters. 



Among them, perhaps, may be ranked the race ofPlanaria one that 

 had been totally overpassed until a very recent era. 



"But having previously submitted my earlier observations on several 

 species to the learned, and the subject having been since infinitely better 

 treated in the works of Dr James Rawlins Johnson, Professor C. Baer 

 of Koningsberg, and M. Duges, only a few supplementary remarks and 

 figures shall be inserted here. 



Ennurneration of species, under the correction which may be effected 

 with time and observation, will add to the Fauna of Scotland. 



Transition from the simple Vermes to the Planaria seems to be 

 direct and immediate, whether from those comprehended in the genus 

 Gordius, or from those associated under the less definite name of Vermi- 

 culi. In the present state of knowledge, I believe that it can be scarcely 

 determined where they meet. 



It is not only difficult to give a satisfactory definition of the genus 

 Planaria, but to specify the subdivisions into which it may be parti- 

 tioned, their perishable, soft, unmanageable, and generally opaque bodies, 

 prove a formidable barrier to the operations of the microscopist and the 

 anatomist. Thus the ordinary observer, in default of better guides, has 

 often to rely on the external form and habits of his subject. 



This, however, will not protect him from erroneously adopting the 

 young of many Vermes as adult Planarice ; nor from classing as inmates 

 of the tribe the planulae of Zoophytes destined to undergo a remarkable 

 metamorphosis. 



