152 SYDNEY J. HICKSON AND J. T. WADS^YOKTH. 
have found in getting Dendrosoma to feed may to some 
extent account for the absence of Tinctinkbrper. 
The contractile vacuoles occur at irregular intervals on the 
arms and may also occur in the stolons, but they are not easily 
seen except in those parts which are relatively free from the 
encrusting dirt (text-fig. A, cv.). The description of these 
structures given by Levick and Kent is correct ; the elongated 
contractile vacuole figured by Claparede and Lachmann is 
obviously incorrect. 
The Meganucleus. 
In a stained preparation of Dendrosoma the meganucleus 
usually appears as a dark band running along the axis of thp 
arms and stolon. It is rarely exactly in the centre, but 
usually bends first to one side and then to the other, or runs a 
course for the whole length of an arm somewhat to one side of 
the exact axial line. In the younger parts of a stolon it has 
very much the same appearance as it has in an arm, but in the 
older parts it is frequently contorted, sometimes broken or dis- 
continuous, branched, or knobbed, and not infrequently 
dissijjated (tigs. 11, 12, 13, and text-fig. A). 
There is so much variation, however, in the general 
character of the meganucleus that it is impossible to describe 
it adequately in a single sentence. 
Although it is usually lound to some extent in every arm it 
never extends to the distal extremity as it is drawn in the 
figures given by Lang and Calkins, and in the younger and 
shorter branches there may be no part of the meganucleus at 
all (text-fig. A). We have observed a difference, which 
appears to be constant in this respect, between the specimens 
fi’om the Bridgewater canal and those from Birmingham. 
In the former the meganucleus extends only a short distance 
into the arms, in the latter it extends very much further ; but 
in this respect, as in others, the meganucleus is subject to 
considerable variation. In many specimens the limits of the 
meganucleus are very clearly defined, in others the boundary 
