No. 634] SHORTER ARTICLES AND DISCUSSION 449 



family within the family Strongylidae ; I am sorry to disagree 

 with him, however, on fundamentals. He bases his argument on 

 four statements : 



1. These worms live in the same organ. However, so do many 

 other worms, trematodes, cestodes, and so forth. 



2. They have identical habits and attach themselves to the 

 mucous membrane in the same manner. The true situation is 

 clearly set forth in Looss's (1905) monograph on the hookworm 

 and in my paper on Camallanus americanus. Ward (1917) has 

 called attention to the fundamental structural difference in the 

 buccal apparatus of the Strongylidaa and I have pointed out the 

 various methods of attachment to the mucous membrane. The 

 members of the genus Camallanus are blood suckers ; this may be 

 true of some strongyles, but not of the hookworm. Looss has 

 shown clearly that it is not a blood sucker and gets blood only 

 incidentally as it feeds on the mucous membrane of the host. 



3. The muscular pharynx or upper part of the esophagus is 

 essentially the same in both types. This part of the esophagus is 

 the same in all the Myosyringata. 



4. The structure of their mouths MacCallum believes to be 

 essentially the same. Ward and I have called attention to the 

 basic fact that the mouths of the strongyles are built up on the 

 circular plan, that they hold fast by suction and then shave off 

 the mucous membrane with additional structures, such as in- 

 ternal cutting plates of the hookworms. In the genus Camallanus 

 the mouth is built up on a lateral plan. The valves are in truth 

 jaws and bite; suction is secondary and is produced, as in all 

 Myosyringata, by the action of the esophagus. 



It would lead me too far astray to take up all the differences 

 between the families Camallanidae and Strongylidae because they 

 even belong in different superfamilies, but I may point out the 

 fact that the former are viviparous forms, while the latter are 

 oviparous, that the Camallanidae have but one single ovary and 

 the males genital alae, while in the other family the females have 

 two ovaries and the males have bursa?. These are such im- 

 portant facts in the structure of nematodes that were there no 

 other points of difference, such as the double character of the 

 esophagus in the Camallanidae, the heavier character of the 

 spioula, and the lack of gubernacula, that they could not be con- 

 sidered in the same subdivision. 



I must call the reader's attention to the following points in 

 MacCallum 's brief description of the genus Camallanus: 



