[Annals N. Y. Acad. Sci., Vol. XVI, No. i, pp. 1-64, February 8, 1905.] 



THE HISTORY OF THE GERM CELLS IN 

 PEDICELLINA AMERICANA (LEIDY). 



Louis I. Dublin. 



Contents. 



(With PL I, II, III, and 2 figs, in text.) 



PAGE 



Preface 2 



I. Material and Methods 3 



II. Sex Relations Within the Colony 4 



III. Spermatogenesis 8 



a. The Character of Testis and Extrusion of Spermatozoa 8 



b. The Several Generations of Spermatogonia 9 



c. The Last Spermatogonial Division and Synapsis 10 



d. The Longitudinal Split in Chromosomes 12 



e. The Formation of Parallel Rods 12 



f. Concentration 13 



g. The Maturation Divisions , 14 



//. The Formation of Sperm 16 



IV. Oogenesis 17 



a. The Structure of Ovary 18 



b,. The Generations of Oogonia 1 8 



c. Synapsis 19 



d. Growth -period of Chromosomes and Longitudinal Splitting 21 



e. Formation of Parallel Rods and Concentration 24 



f. The Maturation Divisions 25 



V. Fertilization and Cleavage 31 



VI . Comment 32 



A. The Individuality of the Chromosomes "^"^ 



B. Reduction 34 



C. Post Synaptic Processes 40 



D. Maturation Divisions 44 



E. Comparison of Oogensis and Spermatogenesis 48 



Summary 49 



Bibliography ... 5° 



Explanation of the Plates 5^ 



1 



