CONTENTS. 



PAGE 



I. Studies on the Hybridization of Echinoids, Cidaris tribuloides. By David 



H. Tennent. 3 plates, 28 figures 3-20 



Part I. Embryology and Hybridization of Cidaris 3 



Nature and Systematic Position of the Material 3 



Early Development of Cidaris trihvloides 5 



Rate of Development of Cidaris compared with that of other Echinoids . . 6 



Comparison with other Investigations of Cidaris 9 



Formation of Mesenchyme in Echinoderms 1 1 



Observations on Hybridization of Cidaris 13 



Influence of Spermatozoon on Production of Paternal Characters 15 



The Spermatozoon and FertiHzation 16 



Cross-Activation versus Cross-Fertihzation 17 



Classification of Hybrids 18 



Part II. Cytology of the Eggs of Cidaris tribuloides and of Cross-Activated 



Cidaris Eggs 21-42 



Structure of the Cidaris Egg 21 



Study of Chromosomes in Species-Fertilized Cidaris Eggs 23 



Chromosomes in Cidaris Eggs Cross-Activated by Lytechinus Sperm 27 



Chromosomes in Cidaris Eggs Cross-Activated by Tripneustes Sperm 29 



Elimination of Chromosomes 32 



Alteration in Physical Characteristics of the Cytoplasm of the Egg by 



Action of Foreign Sperms 34 



Nuclear Enzymes and Cytoplasmic Substrate 35 



The Binuclearity Hypothesis 35 



Discussion 37 



Summary 40 



Conclusions 4j 



Literature 42 



II. The Production of Ldght by the Fishes Photoblepharon and Anomalops. By E. 



Newton Harvey. 1 figure 43-60 



General Account of the Fishes 45 



Histology of the Light-Organ /. . 48 



Lack of Oxygen 5I 



Desiccation g2 



Dilution ' | 53 



Duration of Luminescence 53 



Lucif erin and Luciferase 54 



Temperature ' 55 



Spectrum and Intensity 55 



Cy tolysis 56 



Sodium Fluoride 57 



Potassium Cyanide 57 



Culture Experiments 58 



Summary en 



Literature ." gQ 



III. Hydrogen-ion Concentration and Electrical Conductivity of the Surface Water of the 



Atlantic and Pacific By Alfred Goldsborough Mayor. 3 charts. .61-85 



Observations gc 



Literature cited or 



Explanation of the charts .........". 85 



IV. Carbon-Dioxide Content of Sea-Water at Tortugas. By Roger C. Wells. 1 fig. . . 87-93 



Introduction and Summary of Results gg 



Methods g'j 



General References g3 



III 



