THE APODIDtE part i 



majority of our leading zoologists, but there are diffi- 

 culties not yet explained which make many restless, 

 and lead them to search in other directions. 



In this state of affairs it will be a clear gain and 

 encouragement if we can connect the Annelida and 

 the Crustacea in the way described in these pages, in 

 which we show how a typical carnivorous Annelid 

 (presumably a Nereid, though probably not so 

 specialised as any modern member of that family) 

 can, by a simple and natural adaptation to a new 

 manner of life, be established as the ground type 

 of Apus. We mean a great deal by this expression 

 "ground type," much more than any mere general 

 resemblance of organisation ; we mean that every 

 single organ of Apus, where it does not resemble 

 that of its Annelid ancestor, is capable of being 

 deduced from some organ in the latter, and, further, 

 that the causes of the transformation are not far to 

 seek. These are large claims ; the following pages 

 will show whether they are justifiable. 



Before entering into the morphological and 

 anatomical details upon which our deduction of the 

 Apodidse from a carnivorous Annelid is based, it 

 will make the task of the reader lighter if we here set 

 out the line of argument. 



Many carnivorous Annelids have, as is well known, 

 a protrusible pharynx, armed with teeth, which is shot 

 out for the seizing of prey. We assume that the 

 Annelid from which Apus is derived, adopted a 

 habit of browsing, which rendered this protrusible 



