252 MYRIOPODA. 



glands iii the Myriopoda and Peripatus, is identified with that of the homology 

 of the mouth-parts in the two groups. These glands, in Peripatus, belong to 

 the segment of the oral papillae, and the question of the co-relation of these 

 appendages to the mouth-parts of the Myriopoda will be discussed at the end 

 of this volume. 



In itself, the origin of the salivary glands out of the mesoderm does not appear 

 to us very probable. The Myriopoda, moreover, possess several pairs of these 

 glands (Hekbst, No. 9) occurring in the individual cephalic segments, just as 

 the pairs of salivary glands in the Insecta are distributed on the segments of the 

 mandibles, the maxillae and the lower lip. Nothing appears more likely than 

 that the structures in the Insecta and in the Myriopoda are homologous. It is 

 indeed possible that, as in Peripatus, glands of mesodermal origin may occur 

 side by side with those of ectodermal origin. It would therefore be of primary 

 importance to establish accurately the manner of development of these glands. 



If the salivary or cephalic glands (Herbst applies these two names indifferently 

 to them since spinning glands also are found among them) are of ectodermal 

 nature, they would have to be regarded as crural glands. Such glands (probably 

 ectodermal) are also often found on the trunk in the Myriopoda, and have been 

 compared to the crural glands of Peripatus, and further, to the parapodial glands 

 of the Annelida. In the Myriopoda these glands vary greatly in character. 

 They are described in detail by Eisig (No. 2), who is disposed to regard the 

 protective glands which were described above, according to the accounts of 

 Metschnikoff and Heathcote, as ectodermal, as transformed nephridia. 



The Genital Organs. 



The little that is as yet known as to the formation of the genital 

 organs relates to the genital glands of the Diplopoda. These, as 

 in Peripatus, proceed from the somatic or inner part of the primitive 

 segments, which, however, is not, as in Peripatus, shifted towards 

 the dorsal side, but remains in a ventral position. A large number 

 of primitive segments is used in the formation of the genital glands. 

 The somatic part of these segments shifts towards the median line 

 and comes to lie above the ventral chain of ganglia. The coelomic 

 sacs of the right and left side of each segment come into contact 

 in the middle line. About the time when the embryo hatches, the 

 two fuse so that a single cavity results, and as the consecutive 

 coelomic sacs also unite, a long tube is formed lying between the 

 ventral chain of ganglia and the intestine. This is the genital tube. 



We have no altogether reliable accounts of the relation of the genital tube 

 to the efferent ducts. In Peripatus, the efferent ducts are known to correspond 

 to a pair of nephridia and open out posteriorly. In the Myriopoda, a special 

 interest attaches to this question, because the genital organs in the Chilopoda 

 open posteriorly (on the penultimate segment), in the Diplopoda, on the other 

 hand, somewhat far forward (behind the second pair of legs). "We are inclined 

 to regard the arrangement in the Chilopoda as the more primitive, and to 

 assume a secondary displacement of the efferent ducts in the Diplopoda, a 

 process which can best be explained through the utilisation of another pair 



