ON THE VICTORIAN LAND PLANARIANS. 69 



the worm was seen to be greatly distended just behind the genital opening, and 

 sections showed the presence of a fully formed cocoon occupying the whole of the 

 greatly dilated uterus, and squeezing the other internal organs to one side. The 

 cocoon itself was crowded with closely packed yolk-cells, whose nuclei and outlines 

 were still visible. In older cocoons the yolk disappears as the embryos increase in 

 size until at last the young worms come to occupy the whole of tbe cavity. Finally 

 the young escape through simple rupture of the wall of the cocoon or through a 

 definite circular opening. After having been laid for some time the cocoon appears 

 as an oval or nearly spherical body of a shining black appearance. In the specimen 

 which contained the cocoon in utero the yolk glands were, as might have been 

 expected, very largely developed, and there was some evidence in support of the 

 suggestion which I made in my previous memoir to the effect that the shell of the 

 cocoon is secreted by certain glands opening into the small chamber which receives 

 the contents of the imited oviducts before they enter the uterus. To this chamber I 

 therefore propose to apply the name " shell-gland chamber." 



The brilliancy of colour and markings in the land Planarians are so well known 

 that I need scarcely do more than allude to them. Blue, green, yellow, brown, black 

 and red may be found in various combinations and generally arranged in longitudinal 

 bands or stripes symmetrically disposed on the two sides of the body. It is difficult 

 to account for these varied and brilliant markings, which seem, as I have already 

 pointed out, to be tolerably constant for each species. Wallace proposes* to divide 

 the colours of animals into four groups which he terms Protective, Warning, Sexual 

 and Typical. I would suggest that the brilliant colours of land Planarians may be 

 " warning" colours. There are many butterflies which have been shown by Wallace 

 to be brilliantly coloured and at the same time inedible by birds and there is good 

 reason for believing that the brilliant colours serve to warn the birds of the 

 objectionable character of the butterflies and thus protect the latter from being 

 pecked to death. In the same way I think it possible, though not as yet by any 

 means proved, that the colours of Planarians may serve to protect them from being 

 eaten by birds by rendering them readily recognisable. 



But it requires to be shown first that land Planarians are inedible by or 

 distasteful to birds. I have made two experiments which seem to indicate that this 

 is the case ; (1) I tasted two species myself and found that the mere application of 

 the tongue to the slimy surface of the animal was sufficient to produce an exceedingly 

 unpleasant sensation, something like that caused by putting a piece of velvet or a 

 lump of alum in the mouth. (2) I threw a living specimen of Geoplana spenceri to a 

 number of hens. The hens, not being native birds, would, of course, not recognise 

 the worm, and they at once attacked it, broke it up and took it in their mouths. 



• " Tropical Nature, and other Essays," p. 172. 



