INHERITANCE IN THE ASEXUAL REPRODUCTION 



OF HYDRA 



K. S. LASHLEY 

 From the Zodlogical Laboratory of the Johns Hopkins University 



TEN FIGURES 



CONTENTS 



I. Introduction 157 



Experiments of Hanel 159 



Criticisms of Hand's experiments 159 



Analysis of Hanoi's data 163 



Unsettled questions 165 



II. Variations in Hydra 166 



Variation in the number of tentacles of H. viridis 167 



Conditions producing like variation in parent and ofTspring 170 



III. Existence of diverse races 174 



Experimental methods 175 



Detailed examination of two clones of H. viridis 176 



Differences in number of tentacles and size 176 



Other differences between the clones 182 



Nature of the difference between Clones A and D 183 



Existence of other diverse races 186 



Summary 190 



IV. Inheritance of variations within the clone 190 



Resemblance of close relatives 191 



Effects of selection 195 



Inheritance of size 199 



V. Discussion 202 



VI. Summary 204 



Literature cited 205 



Appendix 208 



I. INTRODUCTION 



The theoretical bearing of the work of Johannsen upon pure 

 lines was not widely appreciated by students of heredity for the 

 first few years after its publication; the general applicability of 

 Mendel's law had not been shown and, hence, the genotype 

 conception was without the support since gained from the evi- 



157 



