. A manual of elementary zoology . Zoology. 260 MANUAL OF ELEMENTARY ZOOLOGY th. 1 A transverse commissure immediately behind the oesophagus joins the two circumoesophageal commissures. It contains fibres which take this roundabout course between the portions of the brain which supply the antennse, thus indicating that these limbs belong to the same series as those behind the mouth. This is probably also true of the anten- nules, and the fact that the antennules and an- tennas are innervated from the supracesopha- n. geal ganglia must be con- nected with the position of the mouth, which, as a
. A manual of elementary zoology . Zoology. 260 MANUAL OF ELEMENTARY ZOOLOGY th. 1 A transverse commissure immediately behind the oesophagus joins the two circumoesophageal commissures. It contains fibres which take this roundabout course between the portions of the brain which supply the antennse, thus indicating that these limbs belong to the same series as those behind the mouth. This is probably also true of the anten- nules, and the fact that the antennules and an- tennas are innervated from the supracesopha- n. geal ganglia must be con- nected with the position of the mouth, which, as a result of cephalisation s. oes. t° a high degree (p. 233), is farther back than in the earthworm, where it lies in front of the first segment. The alimentary canal is supplied by two visceral nerves. The first has a threefold origin, being formed by the junc- tion of a nerve from the cerebral ganglion with two nerves which arise Fig. 165.—A semi-dia- grammatic view of central nervous sys- tem of a crayfish. , , The first and sixth abdominal ganglia; cer., cerebral ganglion; , circumoesophageal com- missure ; /.c, longi- tudinal commissures of ventral cord ; , nerves to abdominal limbs; , nerve to antennule ; , nerve to antenna : , nerve to cheliped ; , nerves to limbs adjoining the mouth ; , optic nerve ; ganglion ; , sternal artery; th. i, 1, first and sixth thoracic ganglia; , nerve to proven- triculus; '., nerve to 71. ah. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Borradaile, L. A. (Lancelot Alexander), 1872-1945. London : H. Frowde, Hodder & Stoughton
Size: 989px × 2528px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, booksubjectzoology, bookyear1920
