. Elements of comparative anatomy. Anatomy, Comparative. VASCULAE SYSTEM OF AKTHKOPODA. 285 ov respiratory organs. Before the blood from them gets to the heart, it passes into the pericardial sinus. In the other Arachnida the many-chambered cardiac tube is reduced, and re- sembles in cha- 0 ° ^^ ^f _*' 6_ racter that of the Insecta. It always lies in the abdo- men; inthcAranea and Opilionida it is provided with three pairs of ostia, by which it is di- vided into cham- bers. From the most anterior of these an artery is continued into the cephalothorax : in Lycosa this is di- vided into two trun
. Elements of comparative anatomy. Anatomy, Comparative. VASCULAE SYSTEM OF AKTHKOPODA. 285 ov respiratory organs. Before the blood from them gets to the heart, it passes into the pericardial sinus. In the other Arachnida the many-chambered cardiac tube is reduced, and re- sembles in cha- 0 ° ^^ ^f _*' 6_ racter that of the Insecta. It always lies in the abdo- men; inthcAranea and Opilionida it is provided with three pairs of ostia, by which it is di- vided into cham- bers. From the most anterior of these an artery is continued into the cephalothorax : in Lycosa this is di- vided into two trunks (Fig. 148), each of which gives off' branches for the eyes and appen- dages. The hin- dermost chamber opens at the end of the abdomen, and the blood-current from it corresponds to that which is distributed by the caudal artery in the Scorpionea. Since | there is no pericardial sinus the blood passes to the respiratory organs, and from them to the heart, by lacunar passages only. Among the Pycnogonida this apparatus is limited to a three- chambered heart, into which two pairs of ostia open; in the Acarina no heai't at all seems to be Fig. 118. Circulatory organs of Lycosa. A Seen from above; B From the side, o Eyes. 1,2,3,4,5,6 Appendages. P Lungs. C Heart, or Venous ostia of the heart. The arrows indicate the direction of the blood (after Clapaivde). Excretory Organs. § 221. The apparatus, which in the Vermes is formed of looped canals, is found in a modified form in the Crustacea. One of the organs, which represent it, consists of a coiled tube placed below the integu- ment of the head, and opening at the base of the second (outer) pair of antennas. In the Entomostraca, this organ is confined to the larva, in which it has been made out in most divisions. It may perhaps be retained in the Cirripedia as the so-called " cement glands/' which lie in the stalk of the Lepadidas, and open at its. Please note that these images are extracted from scanned page imag
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectanatomycomparative
