OCR Text |
Show 208 ON A N HYDEACHNID POUND IN O O E N W A L L . [Mar. 5, Fig. 18. The penial canal, ductus ejaculatorius, and vasa deferentia seen from the side, X 190. Fig. 19. Section through one of the so-called genital suckers and a portion of the adjoining cuticle, X 580. Fig. 20. The great central nervous ganglion (the so-called brain), X 175, showing the various nerves proceeding from it, and the oesophagus passing through it. The entire length of one of the optic and one of the palpal nerves is shown, the other nerves are cut short. Fig. 21. The respiratory organs on one side of the body, X 280, showing tlte sigmoid piece (sp.) with the air-chamber inside, and the connection of the sigmoid piece with the mandible. The tracheal trunk proceeding to the stigma (tra.) is shown, as is also a small portion of the efferent tracheal trunk (tre.). The distal (anterior) portion of the common duct from the salivary glands is seen behind the muscles, and one band of muscle is partly cut away to show the two ducts from the quadrate gland joining the common duct. Fig. 22. One of the palpal organs, X 175. Tbe figure does not include quite the whole of the anterior end of the organ, which extends nearly to the distal end of the palpus. The first joint of the palpus and a portion of the second are shown in section. PLATE IX. Sections. [All the figures in this Plate are drawn from preparations fixed with picro-sulphuric acid and stained with haematoxylin.] Fig. 23. Sagittal median section of rf, X 120. It is a thick section so as to show organs which are not quite in tbe actual median plane if there be not anything in that plane to hide them. The chitinous plates in the cuticle (cp.) are left white, all those in this section are the larger areolated kind of plate, none of the smaller perforated hair-bearing plates come into the median section. Only one dermal gland (dg.) is seen at the anterior end; the section just catches the exterior tunic of this gland, so that it is not really a section of the gland but an exterior view ; sections of these glands are seen in figs. 24, 25. The azygous salivary gland (sa.) and one of the quadrate salivary glands are seen, but neither the reniform nor the tubular salivary glands come into the median section. The oesophagus (02.) is seen passing through the brain (br.). The anterior median portion of the ventriculus ( V.) and its anterior azygous caecum are seen, as is also the hind bridge (vb.) of the organ near the posterior end, but the lateral portions which join the two and complete the hollow square are not seen. The whole length of the excretory organ (E.) is shown ; it contains excretory matter. The whole length of the pharyngeal nerve (nph.) is shown, and just the commencement of the recurrent nerve at the posterior edge of the sub-cesophageal portion of the brain. A small part of the testicular mass (T.) on one side of the body is seen in consequence of its having, from its large size, extended itself over the median line. The whole lengths of the penial canal (P.) and ductus ejaculatorius (de.) are seen, but not the vasa deferentia. Fig. 24. Longitudinal section through a portion of the dorsal cuticle, X 175. The section cuts through some of the larger (areolated) chitinous plates (cp.) and shows that the epiostracum (ep.) is gone from above them. The chitin of the plates is left white except in the areolations, which are mostly filled by living protoplasmic tongues from the cells of the hypoderm (H). Two dermal glands are seen in section, but they have not been cut in the plane which contains the duct; this does not fall into the same vertical plane as the areolated chitinous plates. Fig. 25. Section through one of the anterior dorsal dermal glands, X 175, |