ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 653 



second blood-vessel with specialised contractile walls. These walls 

 consist of a regular series of ring-shaped cells. The vessel, which may 

 be called the dorsal branchial vessel, is capable of undergoing great con- 

 traction and expansion, and, with a contained inner axis, forms a most 

 efficient apparatus for propelling the blood from one end of the vessel to 

 the other as waves of contraction pass down it. There is a com- 

 municating vessel (branchial artery of Vejdovsky and Eietsch) by means 

 of which stoppage of the circulation is avoided on the retraction of the 

 gill filaments, and which affords an alternative path from the main 

 ventral to the main dorsal vessel. 



Polynoid Symbion of HydrocorallinsB.* — Emil von Marenzeller de- 

 scribes a new Polynoid, Lagisca irritans, sp. n., symbiotic on Slenohelia 

 •profunda and Errina macrogastra, sp. n., in the ' Albatross ' collection 

 of 1891. The worm is a typical Lagisca, but the usually strong equip- 

 ment of setas is sparsely represented. 



New Deep-sea Polychsete.t — Akira Izuka describes a new species of 

 Panthalis, P. Mitsukurii, from deep water in Sagami Bay. Nothing is 

 known of the tube, although the presence of spinning glands from the 

 eighth segment backwards indicates the formation of one by this species. 



Memoir on Arenicola.J — J. H. Ashworth has completed in the 

 L. M. B. C. series an excellent memoir on Arenicola. The work includes 

 an account of observations on the development and post-larval stages of 

 A. rtaparedii, a discussion of the affinities of the Arenicolidre, notes on 

 parasitic Trematoda and Sporozoa, an economic section, and directions 

 for practical work. 



Nephridial Cells of Leech.§— L. Fage has studied the nephridial 

 cells of Hirudo medicinalis in various stages of activity. He finds that 

 the active cell is the seat of " ergastoplasmic " formations, which are 

 localised in the basal part of the cell. The nucleus appears to have a 

 role in connection with the " ergastoplasm," the nucleolus probably 

 serving as an intermediary between the chromatin and the cytoplasm. 



Metamerism of Nervous System of Hirudinea.|| — N. Livanow, in 

 a second paper on the morphology of the Hirudinea, deals with the meta- 

 merism of the anterior end of the body, and the innervation of the 

 head region. He observes that in Hirudo there has been much somite 

 reduction, which is manifested almost exclusively in the disappearance of 

 the outer ringing; the main parts^of the nervous system remain un- 

 reduced. The second pre-clitellar segment consists of four rings, the 

 first of which is seen from its innervation to be equal to the first and 

 second ring of the typical 5-ringed somite. The first pre-clitellar has 

 only three rings, the hinder one corresponds to the fourth and fifth, and 

 the front one to the first and second. The fourth somite, which is in- 

 nervated by the sub-cesophageal ganglion, is 3-ringed, with the charac- 



* Bull. Mus. Zool. Harvard, xliii. (1904) pp. 91-4 (1 pi.). 



f Annot. Zool. Japon., v. (1904) pp. 23-9 (1 pi.). 



1 Liverpool Marine Biol. Committee Memoirs, xl. (1904) 118 pp., 8 pis. 



§ Comptes Rendus, cxxxviii. (1904) pp. 1450-2. 



|| Zool. Jahrb., xx. (1904) pp. 153-226 (3 pis.). 



