Morphology of the Myriopoda. 345 
were freshly hatched right from the egg, the larvee are much 
more advanced than in the freshly-hatched larvee referred to ; 
still the second body-segment ts footless instead of the third ; 
but there are seventeen segments, the first, third, and fourth 
each bearing a single pair of legs; the fifth to the tenth seg- 
ments each bearing two pairs of legs. In one of the three 
specimens, which was apparently a little longer out of the egg 
than the two others, there were five penultimate short secon- 
dary segments (eleventh to fifteenth) on which there were 
rudiments apparently of but a s¢ngle pair of legs to each seg- 
ment, whereas Newport states that two pairs bud out from 
each segment, and while in Julus terrestris the new segments 
arise In sixes, in our species they arise in fives. In adult life 
a single pair of limbs arises from the second segment, and the 
first three segments have each but one pair of legs, the fourth 
having two, as in the fifth and following segments. 
It thus appears that the larval diplopod Myriopod is a six- 
footed Tracheate, though neither its mouth-parts nor its pri- 
mary legs are directly homologous with those of the Hexa- 
podous Insects. 
Looking at the embryo diplopod Myriopod from a deductive 
or speculative point of view, it doubtless represents or is nearly 
allied to what was the primitive myriopodous type, a Tra- 
cheate, with a cylindrical body, whose head, clearly separated 
from the hind body, was composed of three cephalic segments, 
one pair of antenna, succeeded by two postoral arthromeres, 
the protomalal and deutomalal arthromeres ; while the hind 
body consisted of as few as seven arthromeres, whose scuta 
nearly met beneath, with three pairs of six-jointed legs distri- 
buted among the first four segments. It 1s evident that the 
form represented by the adult is a secondary later product, 
and arose by adaptation to its present form. The embryo 
Geophilus, the only Chilopod whose embryology has been 
studied, leaves the egg in the form of the adult ; it has, unlike 
the Diplopods, no metamorphosis. Its embryological history 
is condensed, abbreviated. 
But in examining Metschnikoff’s sketches, primitive Chilo- 
gnath characters assert themselves ; the body of the embryo 
shortly before hatching is cylindrical; the sternal region is 
much narrower than in the adult, hence the insertions of the 
feet are nearer together, while the first six pairs of appendages 
(the sixth apparently the first pair of feet of the adult) are 
indicated before the hinder ones. ‘These features indicate 
that the Chilopoda probably arose from a diplopod or diplopod- 
like ancestor, with a cylindrical body, narrow sternites, and 
with three pairs of legs, which represent those of the larval 
