1832.] PLAXARLE. i>7 



beneath logs of rotten wood, on which I believe they feed. In 

 general form they resemble little slugs, but are very much nar- 

 rower in proportion, and several of the species are beautifully 

 coloured with longitudinal stripes. Their structure is very 

 simple : near the middle of the under or crawling surface there 

 are two small transverse slits, from the anterior one of which a 

 funnel-shaped and highly irritable mouth can be protruded. For 

 some time after the rest of the animal was completely dead from 

 the effects of salt water or any other cause, this organ still re- 

 tained its vitality. 



I found no less than twelve different species of terrestrial Pla- 

 nariae in different parts of the southern hemisphere.* Some 

 specimens which I obtained at Van Diemen's Land, I kept alive 

 for nearly two months, feeding them on rotten wood. Having 

 cut one of them transversely into two nearly equal parts, in the 

 course of a fortnight both had the shape of perfect animals. I 

 had, however, so divided the body, that one of the halves con- 

 tained both the inferior orifices, and the other, in consequence, 

 none. In the course of twenty-five days from the operation, the 

 more perfect half could not have been distinguished from any 

 other specimen. The other had increased much in size ; and to- 

 wards its posterior end, a clear space was formed in the pa- 

 renchymatous mass, in which a rudimentary cup-shaped mouth 

 could clearly be distinguished ; on the under surface, however, 

 no corresponding slit was yet open. If the increased heat of the 

 weather, as we approached the equator, had not destroyed all 

 the individuals, there can be no doubt that this last step would 

 have completed its structure. Although so well-known an ex- 

 periment, it was interesting to watch the gradual production of 

 . y essential organ, out of the simple extremity of another 

 animal. It is extremely difficult to preserve these Planarise ; as 

 soon as the cessation of life allows the ordinary laws of change 

 to act, their entire bodies become soft and fluid, with a rapidity 

 which I have never seen equalled. 



I first visited the forest in which these Planarise were found, 

 in company with an old Portuguese priest who took me out to 

 hunt with him. The sport consisted in turning into the cover 



* I have described and named these species in the ' Annals of Nat. Hist.,' 

 vol. xiv. p. 241. 



