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Further Observations on Planarise. By J. R. Johnson, M.D. F.R.S. 

 Read March 10, 1825. [Phil. Trans. 1825,;?. 247.] 



In an account of some species of Planarise, published by Mr. Dal- 

 zell of Edinburgh, that gentleman observed, that in one of these 

 insects which he had intentionally wounded a little below the head, 

 an unnatural prominence soon appeared at the wounded part, which 

 in about four weeks assumed the characters of a new head, and was 

 soon after very distinctly recognised as such. 



Anxious to verify so singular a result, Dr. Johnson took 100 active 

 Planarite cornutae, and made in each an incision on the side of the 

 body. In one instance only he obtained the desired result, in most 

 of them the wounds healed. In some, preternatural excrescences 

 took place, and others separated at the place of incision to become 

 two animals. One only acquired a double head. It appears, there- 

 fore, to be so unusual an occurrence as to deserve the attention of 

 the Royal Society. 



Dr. Johnson proceeds to some additional observations respecting 

 the propagation of certain species of this curious tribe of insects. In 

 regard to the Planariee cornutec, he found that they were more rapidly 

 reproductive by the detachment of fragments when kept singly than 

 when several are preserved in the same vessel, owing, he says, to the 

 necessity then existing of continuing the species ; hence he also in- 

 fers, that the regenerative process is voluntary. The Planaria? kept 

 together, ultimately threw off as many reproductive portions as the 

 others, and these he thinks may probably amount to about 20 in 

 eight months for each insect. The smallest visible portion detached 

 from the tail becomes a perfect Planaria, but in this case the animal 

 is so small as to suggest the probability of the parent animal being 

 viviparous. Dr. Johnson concludes this paper with some observa- 

 tions on the Planaria nigra, the details of which are illustrated by an 

 annexed drawing. Like the species formerly described, it is furnished 

 with an abdominal proboscis, by which it takes its food; it is oviparous, 

 each producing from 2 to 6 young ; it does not spontaneously divide 

 into regenerative portions like the Planaria cornuta, but has an equal 

 power of repairing mutilated parts. 



On the Influence of Nerves and Ganglions in producing Animal Heat. 

 By Sir Everard Home, Bart. V.P.R.S. presented by the Society for 

 the Improvement of Animal Chemistry. Read March 17, 1825. 

 \_Phil. Trans. 1825, p. 257.] 



Sir Everard begins this paper by adducing several instances of the 

 existence of brain and nerves in animals, which however have no 

 power of generating heat ; this is the case with the Oyster, the Snail, 

 and the Water-muscle. In the Leech, the Earthworm, and the insect 

 tribe generally, the nervous filaments are united at intervals by gan- 

 glions ; and where these exist, the temperature exceeds that of the 

 atmosphere when below 56, though in very different degrees, the 



