ARTIFICIAL PARTHENOGENESIS IN THALASSEMA 



MELLITA 



BY 



GEORGE LEFEVRE 



With Six Plates 



I Introduction 91 



II Artificial Parthenogenesis in Annelids 93 



III Material and Methods 97 



IV Experimental Results 98 



1 Acids as Parthenogenetic Agents 99 



2 Artificial Membrane-Formation and Parthenogenetic Development 104 



V Observatious on the Living Material 109 



1 The Unsegmented Egg 109 



2 Formation of Polar Bodies no 



3 Cleavage 112 



4 Formation of Later Embryo and Larva 114 



5 Abnormalities of Cleavage and Behavior 116 



VI Obsevrations on the Preserved Material 119 



1 The Oocyte and the Maturation Divisions 1 20 



2 Origin of the Cleavage Nucleus and Amphiaster 124 



3 The Cleavage Stages 1 25 



4 Gastrulation and the Formation of the Trochophore 127 



5 Rudimentary Cells 129 



6 Abnormal Maturation Phenomena 130 



a Absence of the Second Polar Body 1 30 



h Absence of Both Polar Bodies 132 



7 Abnormal Mitoses 1 34 



a Multipolar Mitoses . , 134 



h Giant Bipolar Figures 135 



c Monasters 136 



VII General Considerations 137 



1 Differentiation without Cell Division 137 



2 Origin of the Cleavage Centrosomes 1 40 



3 Numerical Relations of the Chromosomes 142 



Summary 144 



Literature Cited 146 



I INTRODUCTION 



In two brief abstracts ('05, '06) I have published a few^ of the 

 results v^hich have been obtained from a study of artificial par- 

 thenogenesis in the echiuroid, Thalassema, mellita (Conn). I have 



The Journal of Experimental Zoology, vol. iv, no. i. 



