TRACHEATA. 387 



post-oral appendages) of the Chilopoda (on account of the 

 poison-glands which he thinks may be homologous with the 

 mucous glands). 



The arguments for either of these views do not appear to me con- 

 clusive. There are glands opening into various anterior appendages in 

 the Tracheata, such as the poison glands in the Cheliceras (mandibles) of 

 Spiders, and there is some evidence in Insects for the existence of a gland 

 belonging to the first pair of maxillae, which might be compared with the 

 mucous gland of Peripatus. For reasons already stated I do not regard 

 the processes of the cephalic lobes, which form the lips, as a pair of true 

 appendages. 



BIBLIOGRAPHY. 



(396) H. N. Moseley. "On the Structure and Development of Peripatus 

 capensis." Phil. Trans. Vol. 164, 1874. 



MYRIAPODA 1 . 



Chilognatha. The first stages in the development of the 

 Chilognatha have been investigated by Metschnikoffand Stecker, 

 but their accounts are so contradictory as hardly to admit of 

 reconciliation. 



According to Metschnikoff, by whom the following four 

 species have been investigated, viz., Strongylosoma Guerinii, 

 Polydesmus complanatus, Polyxenus lagurus, and Julus Mone- 

 letei, the segmentation is at first regular and complete, but, 

 when the segments are still fairly large, the regular segmentation 

 is supplemented by the appearance of a number of small cells at 

 various points on the surface, which in time give rise to a 

 continuous blastoderm. 



The blastoderm becomes thickened on the ventral surface, 

 and so forms a ventral plate 2 . 



1 The classification of the Myriapoda employed in the present section is 



I. Chilognatha. (Millipedes.) 

 II. Chilopoda. (Centipedes.) 



2 Stecker's (No. 400) observations were made on the eggs of Julus fasciatus, Julus 

 foetidus, Craspedosoma marmoratum, Polydesmus complanatus, and Strongylosoma 

 pallipes, and though carried on by means of sections, still leave some points very 

 obscure, and do not appear to me deserving of much confidence. The two species of 

 Julus and Craspedosoma undergo, according to Stecker, a nearly identical develop- 

 ment. The egg before segmentation is constituted of two substances, a central proto- 

 plasmic, and a peripheral deutoplastic. It first divides into two equal segments, and 

 coincidentally with their formation part of the central protoplasm travels to the 



25 2 



