NO. 1788. NORTH AMERICAN ER0A8ILIDJE— WILSON. 277 



In the interpretation of the other mouth-parts the literature 

 dealing with this family has shown a wide divergence of opinion, 

 due to a variety of causes. We may first mention the excessive 

 minuteness of these appendages and the accompanying opacity 

 of the cephalon. They are so small that it is practically impossible 

 to make any dissection that will reveal the relation of the parts. 

 One is compelled to study them actually in place and the opacity of 

 the cephalon proves a serious obstacle. If the copepod be flattened 

 sufficiently to push out the contents of the cephalon and let enough 

 light through to render the mouth-parts visible, the latter are prac- 

 tically certain to be twisted or folded out of their natural shape. 

 Furthermore most of the investigators have worked with preserved 

 material in which such methods were impossible. Again, as Mr. 

 Andrew Scott, esq., of the Fisheries Board of Scotland, who has 

 done much excellent work upon both parasitic and free-swimming 

 copepods, has well said in a letter to the author: "It has simply been 

 a case of 'follow my leader' with many writers." They have either 

 been unable to personally examine these mouth-parts, or they have 

 come to such an investigation with preconceived ideas of what 

 ought to be found, and of course have been unable to see anything 

 else. 



Some of them have had the good sense to content themselves with 

 a very meager notice of the mouth-parts thus examined, or have 

 even said nothing at all about them. But others have felt obliged 

 to describe in some detail these organs which they have seen only 

 in figures, or have examined through "colored spectacles." 



Then there has been trouble arising from the degeneration of the 

 mouth-parts, and the consequent abortion or disappearance of some 

 of them. In the Ergasilinse the maxillipeds have entirely disap- 

 peared in the female, while the first maxillae are so rudimentary as to 

 require careful search to detect them. In the Bomolochinse the 

 maxillipeds are abortive in position, and the first maxillae are again 

 so rudimentary as to have escaped the observation of such investiga- 

 tors as Heller, Bassett-Smith, and others. In the genus Tucca 

 none of the mouth-parts have ever been described or figured. 



In the TseniacanthinaB the maxillipeds are often fused so thoroughly 

 to the head as to be immovable, while the first maxillae are as 

 degenerate as in the other subfamilies. None of these causes ought 

 to be effective when acting alone, but their combination has proved 

 very diflScult to overcome. The following table states briefly the 

 name of the investigator, the species described, and the name given 

 to each of the appendages; a blank indicates that the author made 

 no mention of the appendage in question. 



