140 Zoology 



work (Publication 103). The principal activities studied were swimming; reten- 

 tion of habits of reacting to nest, mate, and nest locality, and methods of locating 

 nest (proximate orientation). 



A beginning was made upon the analysis of the sensory factors involved in 

 homing. It was found that both chick and homing pigeon have limits of spectral 

 sensitivity practically coextensive with man's. No support can thus be given to 

 theories of homing which are based upon the use by the birds of infra-luminous 

 light rays. 



This volume also includes the report of an investigation on the acquisition of 

 skill in archery. The special object of the experiment was to test the relative effects 

 of shooting a large number of shots per day or a small number of shots (total 

 amount of practice being the same). It was found that the group shooting the 

 smallest number of shots per day made the greatest gain. 



No. 212. Papers from the Department of Marine Biology of the Carnegie Insti- 

 tution of Washington. Vol. VIII. Octavo, 261 pages, 23 plates, 73 

 figures. Published 1915. Price $3.50. 



This book contains the following papers, not sold separately: 



POTTS, F. A. On the Rhizocephalan Genus Thompsonia and its Relation to the 



Evolution of the Group. 32 pages, 2 plates, 12 figs. 

 POTTS, F. A. Hapalocarcinus, The Gall-forming Crab, with some Notes on the 



Related Genus Cryptochirus. 37 pages, 3 plates, 19 figs. 

 POTTS, F. A. The Fauna Associated with the Crinoids of a Tropical Coral Reef, 



with Especial Reference to its Colour Variations. 26 pages, i plate, 7 figs. 

 CLARK, HUBERT LYMAN. The Comatulids of Torres Strait, with Special Reference 



to Their Habits and Reactions. 29 pages. 



MEDES, GRACE. The Pluteus of Laganum sp. 16 pages, 22 figs. 

 HARVEY, E. NEWTON. The Permeability of Cells for Acids. 14 pages. 

 MAYER, ALFRED G. Medusae of the Philippines and of Torres Straits. 46 pages, 3 



plates, 7 figs. 

 BAHTSCH, PAUL. Report on the Bahama Cerions planted on the Florida Keys. 10 



pages, 8 plates. 

 DAHLGREN, ULRIC. The Structure and Polarity of the Electric Motor Nerve-cell 



in Torpedoes. 44 pages, 6 plates, 6 figs. 



Lieutenant Frank A. Potts, M.A., describes the histology, development, and re- 

 lationships of the highly specialized Rhizocephalan genus Thompsonia from Torres 

 Straits, Australia. 



In another article the same author gives the results of his exhaustive study of 

 the habits of the gall-forming crab Hapalocarcinus, which forms so-called "galls" 

 among the branches of the coral Pocillopora. A detailed account of the formation 

 of these galls is given together with the first description of the minute male crab 

 and of another coral-infesting crab Cryptochirus, and other semi-parasitic or 

 commensal forms. The author determines their various hosts and draws conclu- 

 sions respecting their affinities. 



In a third paper Mr. Potts describes the habits and reactions of the Crustacea, 

 echinoderms, worms, and mollusks which are associated with the Crinoids of the 

 Murray Island reefs, and shows that while in general the color of these animals is 

 similar to that of their hosts, there are some striking exceptions, so that protective 

 coloration was not always realized. 



Dr. Hubert Lyman Clark describes 22 species of Comatulids from Torres Straits, 

 7 of which are believed to be new to science. Some of these forms are very 

 sluggish, while others are quite active. They are chiefly vegetable feeders, but also 

 devour protozoana; all are negatively phototactic, and are sensitive to changes in 

 temperature of only 2 C. 



Miss Grace Medes gives a detailed description of the structure and anatomy 

 of the plutetis larvae of a Laganum, which were collected by Professor David H. 

 Tennent in Torres Straits. The larva is bilaterally symmetrical even at a late 

 stage. Early growth is very rapid, the larval skeleton is complex. The amniotic 

 cavity is formed from a central invagination, and the interocoele and hydroccele 

 show interesting peculiarities. 



Dr. E. Newton Harvey presents a notable study of the rates at which various 

 acids penetrate the living cells of a holothurian Stichopus ananas, the pigment of 

 which is normally purple but becomes red when the cell is penetrated by an acid. 



