AXH'HOR'a ABSTRACT OF THIS PAPER ISSUED 

 BT THE BIBLIOOR.U>HIC SERVICE, OCTOBER 8 



ASSORTIVE MATING IN A NUDIBRANCH, 

 CHROMODORIS ZEBRA HEILPRIN^ 



W. J. CROZIER 



Bermuda Biological Station for Research 



TWENTY-THREE FIGURES AND CHARTS 



CONTENTS 



I. Introductory 247 



II. Mating pairs under natural conditions 249 



III. Measurements 250 



IV. Assortive mating in nature 254 



1. Total length 254 



2. Other measurements 259 



V. Matings in mass experiments 265 



1. Method and findings 265 



2. Comparison with normal conditions 266 



VI. The basis of homogamy 268 



1. Homogamy in Paramecium and in man 268 



2. Mating behavior of nudibranchs 270 



VII. On the consequence of homogamy 278 



1. Number of larvae produced 280 



2. Size 286 



3. Species crossing 287 



VIII. Summary 287 



IX. Postscript 288 



X. References 291 



I INTRODUCTORY 



Observation of copulating pairs of the large nudibranch Chro- 

 modoris zebra Heilprin under natural conditions in the field sug- 

 gested that the component members of a pair tend to be of 

 nearly the same size. Sexually mature individuals of this species 

 which engage in mating at the same time and within a restricted 

 area are found to range in total length from 4 to 18 cms. A dif- 

 ference in the size of two closely approximated specimens is 



1 Contributions from the Bermuda Biological Station for Research No. 98. 



247 



