INTRODUCTION 



Haeckel, in whose laboratory the researches on which 

 the following essay is based were carried out, for the 

 friendly interest he took in them ; and also to Professor 

 Kiikenthal for his cordial sympathy and encourage- 

 ment to proceed in a speculation which claims to 

 solve so intricate a problem as the origin of the 



Crustacea. 



H. M. 13. 



Streatham, 1892. 



