On the Morphology of the Myriopoda. 341 
It seems to us that the researches of Metschnikoff* on the 
embryology of the Chilognaths (Strongylosoma, Polydesmus, 
and Julus) leave no doubt that these Myriopods have but two 
pairs of mouth-appendages, which Metschnikoff designates as 
mandibles and labium. The latter arises as a pair of tubercles 
or buds, at first of exactly the form of the mandibles, and like 
the primitive embryonic mouth-appendages of any arthropod. 
Hence the differentiations of parts and coalescence of the two 
limbs, while closely resembling that of the labium or second 
maxille of Hexapods, really occur in Myriopods in a different 
pair of appendages, 2. ¢. the second instead of the third pair. 
Hence the parts called labium (many authors) in Myriopods 
are really homologous with the first maxille of insects; and 
they should, to prevent misconception, receive a distinctive 
name (deutomale). With the aid, then, of embryology we have 
arrived at a clearer conception of the homologies of the second 
pair of mouth-appendages in the Chilognaths. It forms a 
broad flat plate, becoming the floor of the mouth, and forming 
an under lip; it is differentiated into two sets of broad plates, 
an outer and inner stipes; the outer stipes (stipes exterior) 
bears at the free edge two movable toothed appendages, which 
may be designated as the inner and outer malelle. The inner 
stipes (stipes interior) are united firmly and are supported 
behind by what Meinert designates as the /amina labialis, 
behind which is a curved broad sclerite, called by Meinert the 
hypostoma, a rather unfortunate name, as it has been used by 
Meigen and Bouché for the clypeus of Diptera. Differenti- 
ated from the front edge of the mner stipes is a piece usually 
separated by suture, which, as we understand it, is the sécus 
lingualis otf Meinert; it is our malulella. A median portion 
of the deutomala has been apparently overlooked by authors ; 
it is our labiella (fig. 2), and corresponds in a degree to the 
lingua of Hexapods; it is a minute rounded piece situated 
between the malulelle, in Ju/us minute and single, in the 
Lysiopetalidee much larger, and divided into a large anterior 
and a much smaller posterior crescent-shaped part ; it is sup- 
ported by two long cylindrical divaricating styles. 
It thus appears that the head of Chilognaths bears but 
three pairs of appendages, viz. the antenne and the mouth- 
appendages, the proto- and deutomale. Without doubt the 
Chilognaths, as proved by their embryology and morphology 
and their close relationship with the Pauropoda, the simplest 
Myriopods, represent the primary form of the Myriopods, 
* «“Embryologie der doppeltfiissigen Myriapoden (Chilognatha),”’ yon 
Elias Metschnikoff, Zeitschrift fur wissenschaftl. Zoologie, xxiv. p, 253 
(1874). 
