474 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
other internal organs previously mentioned. It shows little trace of 
the longitudinal division into two parallel cords so evident in the Chilo- 
pods and also shows a very indefinite segmentation. There are two 
problematic appearances to be seen (not in all cases) on the outside 
of the body on the anterior part of the head. They are well drawn by 
Grassi. He considers them to be a pair of eyes even though they are 
not subtended by optic lobes of the brain. 
The animal breathes by means of two tracheal systems which are 
found in the head and possibly the first two somites. Behind these 
somites the conjecture that the coxal sacs serve as respiratory organs 
by allowing the passage of oxygen through their exceedingly thin walls 
is a very happy one. There seems to be an imperfect sac at the base 
of the second coxa and thereafter there are ten perfect pairs near the 
third to the twelfth pair of legs inclusive. 
Musculature. 
The dorsal and ventral musculature is made up of small muscle 
bundles which originate on and are inserted on the tergites or sternites. 
On the dorsal side the distance between the origin and the insertion 
of these muscle bundles is usually the width of one, two, and even three 
dorsal scutes. 
The ventral longitudinal muscle band is double, being parted in the 
mid-line bv the nerve cord and its surrounding tissue. 
The musculature of any two adjacent somites is quite similar. 
According to Gegenbaur ( 78 ): “Where metameres are similar the 
muscles are similar.’’ This similarity is especially well shown in the 
case of the leg musculature. There are five principal sets of muscles 
which are inserted on the coxa (trochanter, Hansen) of each leg except 
at the extreme anterior or posterior ends. These five different muscles 
can be seen on legs 4 to 10 inclusive (pi. 37, fig. 6). 
Two of these originate anteriorly, two posteriorly, and one is nearly 
vertical as seen from a side view. One of these muscles comes from 
the opposite side of the dorsal scute, crossing the body diagonally. 
Muscles were not seen to run forward from the coxae of the first or 
second pair of legs and but a single one forward from the third coxa. 
The eleventh coxa shows but three muscles and the twelfth but one 
and that originates anteriorly. The hinder legs seem to drag rather 
than to step as the animal moves forward. These muscle bundles 
