53 6 THE ANIMAL KINGDOM. 



cyanide and oil of bitter almonds. In Glomeris the secretion is sticky and 

 probably serves to retain the animal in a rolled up condition when it falls. 

 Geophilus Gabrielis, a Chilopod, has a ventral series of glands, in which a 

 large number of tubules open on a perforated plate. The use of the red 

 secretion is unknown 1 . 



The nervous system consists of a supra- and a sub-oesophageal 

 ganglion with a ventral chain. The number of ventral ganglia corresponds 

 as a rule to the number of somites, and the Diplopoda have two to each 

 tergal ring. The ganglia supplying the appendages of the * basilar segment ' 

 in Chilopoda are fused together. Siphonophora (Diplopoda), the Geophilidae, 

 and Cryptcps (Chilopoda), are blind. Scutigera among Chilopoda has a poly- 

 meniscous eye on each side of the head, other Myriapoda have a number 

 of monomeniscous eyes grouped together in the same position. lulus and 

 Glomeris among Diplopoda are stated to have a monostichous ommateum, 

 and the Chilopoda a diplostichous, though the vitreous layer is evanescent. 

 The eye is apostatic or cup-shaped, but the layer of vitreous cells does not 

 share in the invagination. The visual rods at the sides of the cup are 

 directed inwards more or less horizontally, and there are no pigment cells 

 between the visual rods whether at the sides or base of the cup. Each 

 visual cell is said to support many visual rods in the Diplopoda. Scutigera 

 has a retinulate ommateum, and the visual cells secrete rhabdomeres 

 surrounding a conical vitreous body 2 . Sensory hairs are found upon the 

 antennae, and the apical joint of those organs in some Diplopoda is furnished 

 with sensory structures very similar to the structures found in Insecta. A 

 cavity opens externally in Scutigera between the mandibles and maxillae, 

 and one or more cavities beneath or near the eye in some Diplopoda. Their 

 function is unknown, but the presence of hairs within the cavity of Scutigera, 

 and of a single moveable hair in the cavities of Polyxenus lagiirus, point 

 perhaps to that of hearing. 



The digestive tract has a short stomodaeum with salivary glands 3 , a 

 long straight mesenteron, disposed however in a single longitudinal fold 



1 One of the English Scolopendridae discharges a phosphorescent fluid on irritation. Some 

 Chilopoda possess two phosphorescent spots upon the head (Belt, Naturalist in Nicaragua, 1874, 

 p. 141). 



2 The corneal hypodermis ( = vitreous cells) is perhaps always present in development. The 

 horizontal position of the visual rods or of those placed near the rim of the cup may be due, as 

 suggested by Patten, either to the collapse of a vesicle through the action of reagents, or to the 

 lamination of a vitreous body. The rods ( = retinidia) of the basal cells in the eye of Lithobius, as 

 figured by Grenadier, appear to be terminal, and to constitute a retineum. The conical vitreous 

 body of Scutigera is probably to be interpreted as a compound retinidium surrounded by several 

 circles of retinulae. See Patten's general remarks on the Arthropod eye, pp. 665-688, Mitth. Zool. 

 Stat. Naples, vi. 1886 ; and for significance of terms, p. 492 of this book and the note p. 452. The 

 structure of the Myriapod eye needs re-examination. 



3 The Myriapod 'of the division Stigentia' 1 ( = Folyzonidae] 'of Brandt,' mentioned by Belt, 

 op. cit. supra, p. 140, which discharges a viscid fluid over its prey, is a species of Peripatus : see 

 Moseley, A. N. H. (5), iii. 1879, p. 265. 



