MOVEMENTS, ETC., OF FRKSH-WATER PLANAllIANS. 525 



tliose of tlio species of Plauaria, is a form Avliich agrees 

 witli tlie description of Dendrococluni lacteum, except in 

 respect to the colour. This form is usually coloured from a 

 light grey to nearly black. The colouring is uniform. In 

 only one specimen have I found any deviation from this 

 typical coloration, and in that case there Avas a band of 

 black pigment extending the whole length of the body 

 along the mid-dorsal line. In width tliis band occupied about 

 one third the whole width of the body. The margins were a 

 pure white, without the faintest trace of pigmentation. This 

 specimen was kept under observation for some time, and 

 there was no doubt that it belonged to the same species 

 as the grey form. The specimen struck one at once as being- 

 transitional between the ordinary white to cream-coloured 

 Dend rocoelum lacteum, and the grey form found about 

 Ann Arbor. Being in some doubt as to the true taxonomic 

 position of this grey species, I shall refer to it throughout 

 this paper as Dendrocoelum, sp. 



Besides the forms mentioned, several undetermined triclads 

 have been collected and worked with to some extent, but as 

 no new factors presented themselves in their reactions they 

 will not be considered in this papei'. 



Alargei'habdocoele, which I have identified asMesostoma 

 personatum, 0. Schm., is found rather commonly in certain 

 localities about Ann Ai-bor in the spring. I have done some 

 woi'k on this form. Another rhabdoco?le whose actions I 

 have studied to some extent is Stenostoma leucops, O. 

 Schui. No detailed investigation of the behaviour of the 

 vhabdocosles was made, Init as opportunity offered they were 

 used for comparison. 



The methods used in experimentation will be given under 

 the separate headings dealing with the reactions. 



T). Habits^ and Natural History. 

 In the course of more tlian two years' study of planarians 



' In tills section the word " habit " will be used to signify merely tliose 

 activities of the organisms which are frcquontly ol)served to occur under 

 VOL. 46, PART 4. NEW SERIES. M M 



