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 80, 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 of Planarie—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. Baér 
of Koningsberg, and M. Duges, only a few supplementary remarks and 
figures shall be inserted here. 
Ennumeration 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 snide 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 Planari@; nor from classing as inmates 
of the tribe the planulze of Zoophytes destined to undergo a remarkable 
metamorphosis. 
