1 82 THE APODID^E PART 11 



dant remains of Phyllopods, many of which show 

 such a striking resemblance to the Apodid^e that we 

 are justified in claiming them as nearly related forms. 

 This fact lends distinct support to our argument that 

 Apus is a very ancient form, in spite of the deficiency 

 in its own geological record. 



III. The embryological difficulty is even of less 

 account than the two others. Packard, whose studies of 

 the embryology of Limulus entitle him to speak with 

 authority, states that it is evident that the metamor- 

 phoses are all undergone within the egg, in order 

 that the young may enter at once on the manner 

 of life of the adult. And we may repeat here 

 what has been affirmed in other connections, that 

 it is enough if the embryology of Limulus does not 

 directly and plainly contradict our theory ; we say 

 plainly, because we do not lay much weight on the 

 passing hints which an animal in its development 

 may give as to its ancestors, unless these hints are 

 supported by other evidence. 



If these arc not completely satisfactory answers to 

 the difficulties which stand in the way of any close 

 relationship between Limulus and Apus, they at any 

 rate weaken those difficulties to such an extent that 

 they are of little value in comparison with the positive 

 evidence based upon the anatomical and morphological 

 likeness between the two animals, taken together with 

 all the evidence brought forward in the first Part to 

 show that Apus has retained most of the characteristics 

 of a primitive Crustacean, and, in fact, is as truly an 

 archaic form as Limulus itself. 



