Some Notes on Alcippe lampas (Haxc.). 191 
(chitinized) curved band (see Fig. 8) which evidently acts as a 
spring and by its elasticity counterbalances the muscles which insert 
on it. These muscles one on each side of the animal, originate from 
the strong spur-like chitinous thickening projecting inward at the 
base of the oral cirri mentioned above. They act as protrusores 
of the head. When they contract, the chitinous spring and with 
it the region between the knob and the lip edges (which for con- 
venience’s sake I may be allowed to call “neck”) will be pulled in 
and thus the tip of the head and the oral cirri will be protruded 
from the lips. When it relaxes, the elasticity of the band will 
resume its shape, push the neck out and withdraw the head. The 
stage of contraction of these muscles then causes the varying aspect 
presented by the neck region in different preparations. When 
the muscles are torn the chitinous band is found more or less 
stretched out. 
A strong contraction of these muscles will finally cause the oral 
cirri to beat ventrad, a movement described fully by AURIVILLIUS. 
The remaining six pairs of muscles have to be taken together 
in two groups. The first are the protrusors of the body (p 1—3). 
The first of these (p 7) takes its origin from the wall of the dorsal 
half of the body in that region which I called above the first 
thoracic segment, passes obliquely caudad and dorsad and inserts 
just a little caudad of the knob. ’ 
The second one takes its origm from an arcuate chitinous 
thickening in the body wall which is connected with the above 
mentioned spur at the base of the oral cirri, passes obliquely caudad 
and dorsad, partly crossing the fibres of p J and inserts in the disk 
farther caudad than p/. The third protrusor finally takes its origin 
in the ventral half of the last thoracic segments and is made up 
of a number of slips. The strongest of these takes its origin in the 
ventral half of the fifth and sixth post-discal segments, passes in a 
curve near the median line ventrad of the stomach (the muscles of 
the two sides lying close together), then separating from its mate 
it reaches the lateral side of the body wall, passes in a curve 
obliquely dorsad around the stomach, enters the disk just where the 
first post-discal segment becomes free, intersects with its mate and 
crosses over to the opposite side and finally inserts in the disk near 
its centre. 
This most important slip is joined where it leaves the body by 
other slips which partly take their origin more laterally in the last 
