Dr. Johnson’s observations on the genus planaria. 441 
it, as it were, by stealth, gliding gently underneath it, and 
then projecting and affixing this organ, keeping a firm hold 
until they have concluded their repast. I have seen, at times, 
nearly a dozen preying upon a solitary worm. Fig. 16 repre- 
sents the P. cornutce thus engaged ; at a and b this tube is 
seen projected. What however surprised me, was, to observe 
these animals, for a considerable time after, moving the head 
freely from side to side, still keeping the tube firmly affixed. 
As the worm was yet living, I imagined the sole use of this 
organ to be, that of effectually securing their prey. To be 
convinced of this, I gave them a dead worm, which they 
fastened upon in like manner : the head or mouth of these 
animals remaining, as in the former instances, unattached. 
This singularity could not fail of interesting me, since it ap- 
peared they received their food by this organ, and not by the 
mouth. 
To remove any doubt which might still exist, I cut off the 
head of one of the P. lactece , and to the headless body pre- 
sented, a day or two after, an earth-worm, upon which it soon 
affixed, and then inserted this tube; procuring in this way an 
abundant supply, sufficiently evidenced by the interanea, which 
were not before visible to the naked eye, becoming immedi* 
ately conspicuous. Another P. lactea attached itself also to 
a portion of a large earth-worm, keeping its head the whole 
time detached, as delineated in Fig. 15. Here, also, the in- 
teranea were filled, affording an indisputable proof of nou- 
rishment having been taken in by this organ alone. 
From a number of other experiments I found, that when 
the Planarice were perfect animals, this organ was, while 
taking their food, in constant use ; but in the event of their 
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