226 The American Naturalist. [Mareh, 
cept in the Glomeride) are tufted and unbranched, and the 
thickening of the intima is poorly developed. 
In the Diplopods there are well-developed foramina repug- 
natoria upon the sides of each somite of the body. Such 
structures are absent from the Chilopods (as from the Hexa- 
pods), except in a few Geophilidæ, where repugnatorial glands 
occur, opening by foramina in the mid-ventral line. 
In the Chilopods the reproductive organs consist of paired’ 
gonads situated above the alimentary canal and opening to 
the exterior by ducts which are at first paired, but which later 
unite into a common tube which leads to a single external 
opening situated in the penultimate segment of the body. In 
the Hexapods the conditions are almost exactly the same; the 
gonads are dorsal, the genital ducts unite (except in Ephem- 
eride), and there is a single external opening, always at the 
posterior end of the abdomen. In both Hexapods and Chilo- 
pods the spermatozoa are motile. In the Diplopods there 1s & 
single unpaired gonad, situated beneath the alimentary canal, 
and the genital duct, passing forward, divides into two, each 
of which has its own opening at the bases of the legs of the 
second post cephalic segment. The spermatozoa are quiescent. 
We know so little of the embryology of the Myriapods that 
the aid of development can be had to only a slight extent m 
our comparisons,but the facts which it affords seem importan 
In the Chilopods the embryo escapes from the egg with a 
merous ambulatory appendages, a pair to each somite. The 
same is true of the typical Hexapods, all later observers ag" 
ing that a polypod precedes a hexapod condition. The a 
Diplopod escapes from the egg in a Hexapod condition, aM 
the presence of these six legs has been seized upon as a pre 
of the near association of these forms. An exact comparison, 
however, seems to show that the two are in reality very unlike 
as appears in the following table.” 
? Single in Scolopendra. : 
VAs Sanies is koori of the existence of a tritocerebral segment in the pie 
the comparison can only be made upon the basis of the appendages of the = prove 
the tritocerebral segment should prove lacking in the millepeds, the wan yü 
stronger than it now is. The statement of the Diplopod appendages i 
Heathcote (’88). 
