' '/,' I 'S 1\ { C'EA IXTEG UMENTMUSCULA TURE 



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 Nclnlia hypodermal 

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

 Their position recalls the leg glands of Branchiptix. 



"\Ve 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 Corophiidce ; the unicellular dermal glands scattered in various parts 

 of the body of Urcln'stia ; the scat- 

 tered dermal glands of the Anisopoda 

 (Tanais, Apseudes) ; the hook glands 

 of CaprcllidcK ; 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 Corycccidcc (Copcpoda), 

 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 C'orycccidce 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. 



A continuous dermo-mus- 



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, 

 the interarticular membranes by dotted lines. The 



,,,1__ f,,i _ i i hinges between consecutive segments are marked a. t, 



CUlai tube, such as IS character- Tergal (dorsal) skeleton; paternal (ventral) skeleton! 

 IStlC OI the Worms in general, d, dorsal longitudinal muscles = extensors (and flexors 

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

 ,-t r < muscles = flexors. In B, the row of segments is 



IS wanting in the Crustaceans, stre tched ; in A, by the contraction of the muscle d, 

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



generally. The development sternal interarticular membranes. 



of the cuticular integumental covering into a much firmer exoskeleton 



makes a greater localisation of the musculature possible. 



