108 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



maxilla of Orchesella, Japyx (Meinert, '65, Taf. XIV., Figur 8) and 

 doubtless Campodea. More important, however, is the fact that the 

 tendon of Scolopendrella is comparable with the mandibular retractor 

 (cf. Latzel, '84, Taf. 1, Figur 5, e, and Meinert, '65, Taf. XIY., Figuren 

 5, Ibjf.ijlexur) of Campodea and Japjx, and may be homologous with it. 

 It can be easily understood that, if the terminal lobes in Scolopendrella 

 became immovable by solidification in the mandible, the adductors of 

 those lobes would then serve as retractors of the entire mandible, as in 

 Campodea and Japyx. 



Grassi ('86% pp. 15-lG, Tav. II., Figure 2, 5) supplements Latzel's 

 account of Scolopendrella by saying that no true cardo is present, and 

 that the mandible is capable of lateral movements only. 



Packard ('83'', p. 198) says, "The so-called mandibles of the Myrio- 

 pods are the morphological equivalents of those of insects, but structur- 

 ally they are not homologous with them, but rather resemble the lacinia 

 of the hexapodous maxilla." With the last assertion I do not agree. 

 The mandibles of the more generalized Diplopods are in detail strikingly 

 like those of Scolopendrella (Latzel, '84, Taf. I., Figur 5) ; for example, 

 those of Polyzonium (Latzel, '84, Taf. XVI., Figur 203), in which the 

 only fundamental difference is the presence of a cardo in Polyzonium, the 

 stipes, galea, lacinia, and tendon being essentially as in Scolopendrella. 

 The mandible, or protomala (Metschnikoff, '75), of Polyzonium does, in- 

 deed, resemble, not the lacinia, but the entire first maxilla of Thysanura 

 and Collembola. The similarity, however, should not be mistaken for 

 homology ; it rather serves to emphasize the structural agreement of 

 mandibles and maxillae, — an agreement which gradually becomes ob- 

 scure in the insect series through the progressive solidification of the 

 mandible, but may nevertheless be traced, as I have shown, from Diplo- 

 podaand Symphyla, through Campodea and Japyx, Machilisand Lepisma, 

 to the more generalized Orthoptera ; thus the differences between the 

 mandibles of Diplopods and Insects are not so great as Packard has 

 affirmed ('98, p. 12). 



The most that is known about the development of Diplopod mouth- 

 parts we owe to Metschnikoff ('74), who represents only two pairs of 

 oral fundaments, designated " mandibles " and " labium." Although this 

 conclusion is also reached by vom Path ("86), I would not infer with 

 Packard ('83'', p. 190) that there can be only two pairs of oral appen- 

 dages, but would suggest that embryological studies upon the nioutli- 

 parts of other Diplopoda may, perhaps, sliow more. 



The mandibles, or protomala\ of Cliilojuida are generally recognized as 



