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Nemertina Stock Photos and Images
RMMFGT6Y–Grytviken, the principal settlement in South Georgia, a former whaling station and now a base of the British Antarctic survey
RM2AWG40K–Text-book of comparative anatomy . ic in their arrangement, in cor-respondence with the more or less regular metameric arrangementof the enteric diverticula themselves. In some Nemertina there arealso genital glands scattered about the parenchyma, each gland, however,has an independent external aperture. In this arrangement we findgreat agreement with the Turbellaria (especially the Polyclada andTriclada). In the latter, however, the oviducts and sperm ductsarising from the genital glands unite to form common channels of exit. Nemathelminths.—1. Nematoda.—The male genital apparatus isunpaired,
RFENJE6X–Grytviken, the principal settlement in South Georgia, a former whaling station and now a base of the British Antarctic survey
RMPG407J–. A manual of zoology. Zoology. IV. NEMERTINA 2.55 cellulose of T. solium, found in man, more frequent and of more importance is the cysticercus of Tamia echinococcus (fig. 232), which lives as an adult in the dog, and is easily overlooked on account of its size. It is at most i inch long and consists of a scolex and three or four proglottids. When the eggs are taken into the human stomach, as may easily happen by stroking and kissing infected dogs, the embryos are set free and wander into liver, lungs, brain, or other organs and produce here tumors which, in the case of the liver, may weigh t
RM2AWGGC7–Text-book of comparative anatomy . only need to move together into the ventral middle line, so as tobecome the typical ventral chord of the Annulata. The mouth and oesophagusprevent such a moving together in the anterior part of the body, and so thefirst part of the longitudinal trunks becomes the cesophageal commissures of theAnnulata. An approximation of the longitudinal trunks, which, it is true, never leads to directcontact, may be observed as early as the Nemertina, not to speak of the Platodes.Whereas as a rule among these forms the paired longitudinal trunks lie laterally,sometimes even
RFENJE70–Grytviken, the principal settlement in South Georgia, a former whaling station and now a base of the British Antarctic survey
RM2AWGJ9D–Text-book of comparative anatomy . observe thicker strands, which form annu-lar commissures between the three principal nerves running inthe longitudinal direction. In the Hoplonemertina the nerve sheath iswanting; the commissures run separately, and sometimes show amarkedly metameric arrangement. In the whole structure of this nervous system a considerable agreement with thatof the Platodcs (Polychidu, Tridada, Trematoda) cannot lie ignored. The brain andthe longitudinal trunks of the Nemertina answer to the brain and the ventral longi-tudinal trunks of the PJatodes. Whether the unpaired dors
RM2AWG51B–Text-book of comparative anatomy . 250 COM PA RA TIVE A NA TO MY CHAP. vascular system of the Hirudinea recalls that of the Nemertina. They also agree in the possession of blood sinuses. The vascular system of the Chcetopoda is strikingly different from that of the Hirudinea. It is entirely separate from the body cavity. Both the lateral vessels ofthe Hirudinea are wanting.The most important andconstant parts of the Ckceto-podan circulatory apparatusare : (1) a medio-dorsallongitudinal vessel and (2)a medio-ventral longitudinalvessel (Fig. 165). The firstis mostly contractile ; in itthe blood
RMRE0830–. A text-book of invertebrate morphology. Invertebrates. 162 INVERTEBRATE MORPHOLOGY. IV. Class Nemertina. The three preceding classes show marked evidences of genetic affinity, the characteristic differences of structure in the Trematodes and Cestodes being due to the parasitic habits of these forms. The Nemerteans, on the other hand, though apparently tracing descent from a Turbellarian-like ancestor, show a marked advance in structure, and must be regarded as organisms of a considerably higher grade than the other Platyhelminths. They are for the most jDart marine, though a few forms inhabi
RMRDJ6RN–. A manual of zoology. Zoology. IV. NEMERTINA 2.55 cellulose of T. solium, found in man, more frequent and of more importance is the cysticercus of Tamia echinococcus (fig. 232), which lives as an adult in the dog, and is easily overlooked on account of its size. It is at most i inch long and consists of a scolex and three or four proglottids. When the eggs are taken into the human stomach, as may easily happen by stroking and kissing infected dogs, the embryos are set free and wander into liver, lungs, brain, or other organs and produce here tumors which, in the case of the liver, may weigh t
RMRCJ4AB–. Die Leitungsbahnen im Nervensystem der wirbellosen Tiere. Anatomy, Comparative; Nervous system. NEMERTINA. 41 ganglien, welchen sich zwei nach hinten laufende und durch Kommissuren verbundene Seitenstränge (Fig. 12, s. str.) anschheßen. Hirnganglien und Seitennerven bilden wieder den Ursprung der peripheren Nerven. Dewoletzky (1888) ist der erste, welcher auf einen kleinen Teil des Xervenfaser- verlaiifs hindeutet, wenn er sagt, daß die FHmmerzellen der Wand des Seitenorgans (Fig. 12, s. o.) der Xemertinen durch Fasern mit den Zellen des GangKons, welches das Organ umgibt, in Verbindi.mg ste
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