SECT. XII RELATION OF APUS TO CRUSTACEA 183 



Having prepared the way, let us commence the 

 detailed comparison of the organs of Limulus and 

 Apus. 



The first point on which we fix our attention in 

 order to test the relationship between the two animals 

 may not appear very important, but the longer it is 

 considered the more convincing, it seems to us, is the 

 argument founded upon it. It is as follows : 



Our main argument is that Apus is ■d.bent Annelid. 



Fig. 42.— Secfion oi Lhniiltts rotuiidicauda to show the bend in the intestine with 

 the sinewy sternal plate in the angle to be compared with that of Apus Fig. 13, 

 p. 56. h, brain ; h, heart ; /, openings of the hepatic ducts in the mid-gut ; j/, 

 the sternal plate. From Bronn's Klassen icnd Ordnitn,o^en des Thiej-rcichcs. 



In this way we explained the bend in the intestinal 

 canal which is so characteristic of the Crustacea. 

 This bent intestine is very marked in Limulus (see 

 Fig. 42), and suggests the same origin. This, how- 

 ever, was not enough. We argued that if we find in 

 the bend of the intestine of Limulus a sinewy mass 

 such as we find in Apus, referable there to the 

 clumping together of the abdominal musculature, 

 the coincidence can hardly be a mere case of 

 analogy. Such a sinewy mass is found in Limulus, in 



