BY J. J. FLETCHER AND A. G. HAillLTOK 357 



Those belonging to the genus llhynchodemus seem to be much 

 more delicate than the species of Geoplana ; it is much more 

 difficult to keep them alive for any length of time, and even 

 when handled in the most careful manner, using a feather in 

 moving them, they frequently break up into pieces in the most 

 provoking manner when touched, or on exposure to the light during 

 examination, while in dealing with the species of Geoplana we 

 have had little or no trouble. Though they evidently dislike 

 exposure to strong light, yet sometimes when the tin in which we 

 keep them has been incautiously left uncovered for a short time 

 they have braved the consequences in their efforts to escape. 

 Some have got right away, while others were found by following 

 up their slimy tracks, a few feet off, dried up on the table partly 

 through the dust on it. 



We know nothing definite concerning the enemies whose attacks 

 they have to withstand. In turning over logs in search of 

 planarians, one cannot help noticing the numbers of centipedes, 

 scorpions, spiders, ants, and predaceous beetles which are exposed 

 to view, and of suspecting some or all of them of being at 

 enmity with the planarians. 



Nearly all our species of Geoplana, like many found elsewhere, 

 are conspicuously marked, and some of them brightly and variously 

 coloured. Thus one is blue with a white stripe, two are red, one 

 is grass-green with reddish strijies, another bright yellow with 

 dark stripes, and so on. This is the more remarkable in that they 

 are essentially nocturnal animals. Darwin himself points out that 

 in the case of hermaphrodite creatures such as planarians " the 

 colours do not serve as a sexual attraction, and have not been 

 acquired through sexual selection " (Descent of Man, p. 260). 

 Nor, avoiding the light as they habitually do, is it clear how their 

 colours can be of use to them as a protection either by assimilating 

 them to the colour of their surroundings, or as in the case of 

 gaudy caterpillars by serving as a warning to their enemies that 

 they are distasteful, or that they are provided with defensive 

 structures in the shape of urticatiug organs (rod cells). On the 



