AUTHOR S ABSTRACT OP THIS PAPER IS- 

 STJED BY THE BIBLIOGRAPHIC SERVICE 



A STUDY OF THE CAUSES AND THE EXTENT OF 



VARIATIONS IN THE LARVAE OF ARBACIA 



PUNCTULATA 



GRACE MEDES 

 Bryn Mawr College, Bryn Mawr, Pa. 



ONE HUNDRED AND FIFTY-TWO FIGURES 



CONTENTS 



I. Introduction 318 



II. Literature 319 



III. Methods ^ 328 



IV. Experimental 331 



A. The range of variation in the larvae of Arbacia i)unctulata at 



different seasons 



B. The range of variation in Arbacia larvae subjected to changes in 



the surrounding medium 



1. Changes in the concentration of normal sea-water 



a. Concentration by evaporation 



b. Dilution by addition of distilled water 



2. Changes in the chemical composition of the sea-water 



a. Changes in alkalinity 



aa. Addition of acids 

 bb. Addition of alkalies 



b. Addition of salts 



aa. Isotonic solutions 

 bb. Hypertonic solutions 



c. Addition of carbon dioxide 



C. The range of variations in Arbacia larvae kept under standard 



conditions 



1. Individual variations 



a. Eggs from a single female fertilized with sperm from a 



single male 



b. Eggs from a single female fertilized with sperm from 



different males 



c. Eggs from different females fertilized with sperm from 



a single male 



2. Variations due to staleness of sexual products 



V. Discussion 420 



A. Factors that could not be controlled 



317 



