138 Zoology 



Dr. L. R. Gary has determined the growth rate of various Gorgonians and de- 

 cides that, at Tortugas, hurricanes are the most serious factor interfering with 

 the growth of these animals. The average rate of growth in young specimens is 

 about 50 mm. in height per annum, but it ranges greatly in different individuals and 

 under different environment conditions. 



I>r. Hubert Lyman Clark points out the importance of the study of the develop- 

 ment, growth stages, and paleontological history of the brittle stars in order to 

 determine a natural system for their classification. He then proceeds to present 

 the results of his study of the growth changes in three species of brittle stars be- 

 longing to the genera Ophiactis, Amphipholis, and Ophiothrix. 



Professor David H. Tennent shows that in hybrid larvae between the two echini, 

 the male of Toxopneustcs and female of Cidaris, the sperm shows its influence over 

 the development from the earliest stages of gastrulation and mesenchyme formation. 



Professor Robert Tracy Jackson describes the results from his study of the 

 ocular plates of 2,878 specimens of Echini from Montego Bay, Jamaica; the re- 

 search being an extension of his notable work, the "Phylogeny of the Echini." 



Professor H. E. Jordan shows that there are no accessory chromosomes in the 

 male Mongoose, cat, squirrel, pig, and rabbit, but these are apparently found in the 

 white mouse, sheep, horse, mule, bull, and dog. The accessory chromosome may 

 act as a deterrent to the development of maleness. 



Dr. Raymond C. Osburn describes 76 species of Bryozoa from the shallow water 

 down to 22 fathoms, in the region of the Tortugas, Florida. 8 are new to science 

 and 40 are new to the Florida region. 



No. 183. Papers from the Tortugas Laboratory of the Carnegie Institution of 

 Washington. Vol. VI. Octavo, m+323 pages, 27 plates, 97 figures. 

 Published 1914. Price $3.50. 



This book contains the following papers, not sold separately: 

 MAYEK, A. G. The Effects of Temperature upon Tropical Marine Animals. 24 



MAYER, A'. G. The Relation between the Degree of Concentration of the Electrolytes 



of Sea- Water and the Rate of Nerve-Conduction in Cassiopea. 30 pages, 13 figs. 

 MAYER, A. G. The Law Governing the Loss of Weight in Starving Cassiopea. 28 



pages, i plate, 21 figs. 

 GOLDFARB, A. j. Changes in Salinity and Their Effects upon the Regeneration of 



Cassiopea xamachana. 12 pages, 4 figs. 

 GOLDFARB, A. J. Regeneration in the Annelid Worm, Amphinoma paciftca, after 



removal of the Central Nervous System. 8 pages. 



GOLDFARB, A. J. Experimentally Fused Larvae of Echinoderms with Special Refer- 

 ence to their Skeletons. 20 pages, 15 figs. 



MCCLENDON, J. F. Experiments on the Permeability of Cells. 8 pages, 3 figs. 

 HARVEY, E. N. The Relation between the Rate of Penetration of Marine Tissues 



of Alkali and the Change in Functional Activity induced by the Alkali. 16 



pages, i fig. 

 JACOBS, M. H. Physiological Studies on Certain Protozoan Parasites of Diadema 



setosum. 1 1 pages. 

 DAHLGREN, ULRIC. Origin of the Electric Tissues of Gymnarchus niloticus. 36 



pages, 9 plates, 9 figs. 

 REINKE, E. E. The Development of the Apyrene Spermatozoa of Strombus bt- 



tuberculatus. 46 pages, 7 plates. 

 GUDGER, E. W. The History of the Spotted Eagle Ray, Aetobatus narinari, together 



with a Study of its External Structures. 91 pages, 10 plates, 19 figs. 



Mayer states that tropical marine animals commonly live within 5 C. of their 

 temperature of maximum activity and within 10 to 15 of their upper death tem- 

 perature. Tropical forms are less resistant to temperature changes than are the 

 animals of temperate seas. In tropical Scyphomedusae depression of activity due 

 to heat or cold appears to augment about as the square of the change in tempera- 

 ture above or below the optimum. Temperature is the most important factor in 

 determining the ecological distribution of coral heads of various species over the 

 reefs. High temperature probably causes death through asphyxiation. 



In Cassiopea the rate of nerve conduction in diluted sea-water is determined 

 by the concentration of the electrolytes sodium, potassium, and calcium, and not to 

 changes in osmotic pressure. It makes practically no difference whether the sea- 

 water be diluted with distilled water, 0.9 molecular dextrose, or 0.4 molecular mag- 

 nesium chloride. The sodium and potassium cations are active stimulants for nerve 

 conduction, but magnesium is practically negative, being neither a stimulant nor an 

 active inhibitor of nerve conduction. 



