WATER FROM HOLLOWS ON TREE TRUNKS. 437 



of a more elongated and rectangular shape with a spine arising 

 from near the base on the inner edge, and four spines from the 

 distal edge, the third of which from the inner side turns outwards 

 across the outer spine. None of the spines are of the flattened 

 blunt type present on the fifth foot of the female. 



The spermatophore (fig. 19) is flask or retort-shaped with very 

 thick walls, the outlet tube being embedded for a part of its 

 length in a mass of cementing material.* 



Length without terminal setae, about l/50th in. 



As regards the habits of M. arboricola not very much can be 

 said. They are not very good swimmers, their movements in the 

 open water being best described, perhaps, as an active wriggling 

 assisted by the beating of the feet rather than as true swimming 

 produced chiefly by the action of the feet. On the whole they 

 seem to prefer moving downwards more than upwards when free 

 from support. They can, however, cling very strongly even to 

 glass, and often in this way travel about the sides of the vessel in 

 which they are kept. Very often I have found that they have 

 clung to the inside of the pipette whilst being transferred from a 

 bottle to the live-box. When placed in a watch-glass I have noticed 

 on several occasions that a tap on the glass had the effect of suddenly 

 stopping their movements just as if they were feigning death. 



As already mentioned, M. arboricola has only been found in 

 little hollows on tree trunks in Epping Forest, and so far only 

 in the Theydon Bois and High Beech districts, f The first 

 specimens were found in 1904 near Theydon Bois, and since that 

 date the species has been obtained many times either actually 

 living in the water and sediment or developing out of the black 

 earthy deposit taken from dry hollows and placed in water. It 

 has happened on several occasions that no trace of the animals 

 could be found in the first instance, but that after several weeks,. 



* This peculiar mass can be seen in the same relative position while the 

 spermatophore is still within the body of the male. It seems therefore to 

 be a constant character and not merely a temporary feature produced at 

 the time of attachment to the female. 



t The fact that so many of the Epping Forest trees have been pollarded 

 in bygone times has had the effect of largely increasing the number of 

 cavities and hollows on their heads and trunks in which water can 

 accumulate in wet weather, thus rendering the district a particularly 

 favourable one for the study of the fauna and flora of such a peculiar 

 environment. The systematic investigation of this fauna and flora is much 

 to be desired, and could scarcely fail to vield valuable results. 



