ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 299 



distinction between homology and analogy, and of the relations between 

 form and function. His precise object was to obtain light on what he 

 oalls " the functional heredity " of the limbs of Ligia. 



Each walking-leg of the common littoral Isopod Ligia shows three 

 prominent flexures arranged alternately in one plane. Generally speaking, 

 the planes of flexure of the whole series of seven limbs are transverse to 

 the body, the basipodites flexing medially. This Isopodan limb-taxis is 

 •associated with clinging power. 



In Amphipoda and in Tanaidacea there are likewise three chief 

 flexures in the limb, which are also arranged tri-alternately and in one 

 plane. In the Tanaidacea the basipodites project laterally, not medially. 

 In the Amphipoda the basipodites flex antero-posteriorly. Tanaidacean 

 limb-taxis seems to be the primitive mode. 



The tri-alternate flexion-complex in each limb of these Peracarids, 

 «,s well as in certain limbs of Cumacea, is a reptant feature ; so is the 

 separation of the seven limbs into two opposing groups. The author 

 suggests an analogy with the limbs of reptant vertebrates. By simple 

 inspection it is usually possible to say if a crustacean limb used for 

 swimming has been secondarily modified from a reptant limb. 



The flexion-complex in the limbs of reptant Eucarida is neither 

 tri-alternate nor uniplanar, as in the limbs of reptant Peracarida. This 

 •distinction is of more importance than that suggested by Boas, which 

 xelies upon the amount of flexion possible at the mero-carpal and at the 

 carpo-propodal articulation respectively. 



The Peracarida, like the Decapod Crustaceans, may be divided into 

 natant and reptant forms, with intermediate links. Of the reptant 

 forms only those with Isopodan or Amphipodan limb-taxis have shown 

 themselves capable of adopting a terrestrial life. The different forms 

 of limb-taxis in the Peracarida and certain features involving the flexion- 

 oomplex present problems " analogous " to the rotation and torsion that 

 occur in the fore-limb of a developing mammal. This suggests, indeed, 

 the main interest of this remarkable paper, which we cannot do justice 

 to in summary : the endeavour to re-unite the endeavours of morpho- 

 logical and physiological analysis. 



Antarctic Ostracods.* — Frederick Chapman reports on Ostracods 

 collected on Sir Ernest Shackleton's Antarctic Expedition, from elevated 

 deposits on the shores of the Ross Sea, and from marine muds from 

 soundings in the Ross Sea, Five species of Ostracods were obtained 

 from upthrust muds above the Drygalski Glacier, south-east of Mount 

 Larsen. One of them is new — Cytheropteron antarcticum sp. n. — the 

 others are southern oceanic forms. From elevated deposits on the 

 slopes of Mount Erebus eight species were obtained, including two new 

 species, Loxoconcha mawsoni and Xestoleheris davidiana. The Ostracods 

 from the muds (eleven species, including Cythere davisi sp. n.) represent 

 in the main a southern oceanic fauna. A marked exception is Cytherura 

 rudis, previously known from Spitzbergeu, Greenland, and the Far 

 Korth. 



* Reports Sci. Invest. Brit. Antarc. Exped., Geology, i'. (1917) pp. 37-40 (1 pi ) ; 

 pp. 49-52 (1 pi.) ; pp. 71-5 (1 pL). 



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