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 tribuloides 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 11 



Observations on Hybridization of Cidaris 13 



Influence of Spermatozoon on Production of Paternal Characters 15 



The Spermatozoon and Fertilization 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 36 



Discussion 37 



Summary 40 



Conclusions 41 



Literature • . • 43 



II, The Production of Ldght by the Fishes Phofobkpharon 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 51 



Desiccation 52 



Dilution 53 



Duration of Luminescence 53 



Lucif erin and Lucif erase 54 



Temperature 55 



Spectrum and Intensity 55 



Cy tolysis 56 



Sodium Fluoride 57 



Potassium Cyanide 57 



Culture Experiments 58 



Summary 59 



Literature 60 



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



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



Observations 65 



Literature cited 85 



Explanation of the charts 85 



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



Introduction and Summary of Results 89 



Methods 91 



General References 93 



III 



