Dr. Johnson’s observations on the genus planaria. 445 
a magnified form, the P. brunnea, and Jig. 13, the P. cornuta, 
with renewed heads and tails. The head portions show, 
very distinctly, a circular-like range of black dots close to 
the margin, which I conjecture to be the eyes ; and the tail 
portions show the renewal of the abdominal tube. 
July 30. The Planarice with newly formed heads, men- 
tioned in the first experiment, were again divided, and re- 
produced by August 25 (2 6 days). At the time of the former 
experiment these animals were strong and vigorous, which 
sufficiently accounts for the difference of time in the repro- 
duction. Fig. 14 represents the head of one ( P. torva ) highly 
magnified, showing the eyes in the centre of the white 
areola. 
I afterwards divided these animals into four, five, and even 
six parts ; and what was extremely singular, each part 
seemed to possess the properties of a perfect animal, moving 
about in the water in the same gliding manner as before the 
separation. But when thus divided, they seldom retained 
their vitality beyond a few days, or if any portion did, per- 
chance, recover its lost parts, it was a process extremely 
slow and tedious. 
To render these experiments successful, it will be necessary 
to divide the Planarice immediately on their being taken from 
their native haunts, for, when long confined, they lose their 
activity, and are ill calculated for the purpose. I should 
have observed, that, although the lost parts are generally 
reproduced in about a fortnight, yet a month or more is re- 
quired before they take on the precise form and colour of the 
original animal. 
The Planarice with renewed organs were placed in a vessel 
