CR USTA CEAINTEG UMENT MUSCULATURE 



331 



homologous with the spinning and setiparous glands of the Annelida and the coxal 

 glands of other Arthropoda. 



In the basal joints of the 8 pairs of thoracic limbs of Nebalia hypodermal 

 glands have been observed ; it is probable that these perform excretory functions. 

 Their position recalls the leg glands of Branchipus. 



We may here further mention the dermal glands which occur in the basal joints 

 of certain limbs of the Phronimidce ; and the beautifully constructed dermal glands 

 in the limbs of the CoropJiiidce ; the unicellular dermal glands scattered in various parts 

 of the body of Orchestia ; the scat- 

 tered dermal glands of the Anisopoda 

 (Tanais, Apseudes] ; the hook glands 

 of Caprellidce ; and the so-called 

 cement glands of female Decapoda, 

 which lie on the ventral side of the 

 abdomen, and whose hardening secre- 

 tion serves for the attachment of the 

 eggs. 



In Tanais and the Corophiidce the 

 secretion of the above - mentioned 

 glands hardens in water, and prob- 

 ably helps, by cementing together 

 foreign particles, to form the tubes 



inhabited by these animals. 



Special interest is claimed by the 

 uni- and multi-cellular dermal glands 



lying scattered under the chitinous 



cuticle of the Corycoeidae, (Copepoda), 



because in them the connection of 



the gland cells with nerve fibres can 



be easily observed. A unicellular 



dermal gland with cuticular duct, 



which opens through a pore of the 



chitinous integument of the body, 



is in the Corycceidcc generally coupled 



with a terminal ganglion cell lying 



under a sensory seta. The nerve 



which runs to this pair of cells divides 



into 2 threads, one of which is con- 

 nected with the gland cell and the 



other with the ganglion cell. 



III. The Musculature. 



FIG. 230. Diagrams to demonstrate the 

 mechanism of the motion of the segmented body 

 in the Arthropoda. One larger segment (ct) and 4 

 smaller. The exoskeleton is denoted by black lines, 

 A COntinilOUS derniO-mUS- tne inte particular membranes by dotted lines. The 



Cular tube such a s i s r h. a ra of Pr hinges between consecutive segments are marked a. t, 

 ,UU LUD6, SI Cnaracter- Tergal (dorgal) skeleton . , f sternal (ven tral) skeleton ; 



IStlC 01 the worms in general, d, dorsal longitudinal muscles = extensors (and flexors 



and Specially of the Amiulata in an u P ward direction); v, ventral longitudinal 



i wnnfirrr , f^^ n,,^ ' muscles = flexors. In B, the row of segments is 



S Wanting m the Crustaceans, stre tch e d ; In A, by the contraction of the muscle d, 



and indeed in the Arthropoda bent upwards; in C downwards, tg, Tergal; $g, 



generally. The development sternal interarticular membranes. 



of the cuticular integumental covering into a much firmer exoskeleton 



makes a greater localisation of the musculature possible. 



