182 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



of the animal may become pointed, and hence appear as if it were the anterior 

 extremity, and as fast as the pointed portion shifts the mouth will also apparently 

 change its position, at one moment being apparently at the anterior end, at the 

 apparent posterior end, on the right or left side, or on the dorsal (fig. 2) or ventral 

 surface. In all cases, however, I find the mouth at the pole opposite to the nucleus. 

 Od account of this constant apparent shifting of the mouth in position, I am led to 

 doubt the validity of its apparent position as a specific character, and hence to call 

 into question Zacharias's species, I. cryptostomits, distinguished from I. multifiliis, as 

 we saw above, by the antero-ventral instead of antero-terminal position of the mouth. 

 If we now compare figs. 1 and 2 of Zacharias's species with the statements just made, 

 we see that our statements agree in so far that the mouth and nucleus are opposite 

 each other, for he figures the mouth (fig. 2) as ventral, the nucleus (fig. 1) apparently 

 as dorsal of it, i. e., he has drawn a dorsal view, according to his interpretation of 

 the topography, and in this view the nucleus is anterior. I have seen this same rela- 

 tion dozens of times in the form observed at Chicago. 



Kerbert's figures, 1 and 3, support the statements here made, that the mouth and 

 nucleus are at opposite poles and that the mouth apparently shifts* in position. 



Agreeing with Fouquet and others, I find the mouth round and noncontractile; 

 surrounding the aperture is an area which is thickened slightly and devoid of cilia 

 (others have found the cilia longer in this position than over the rest of the body), but 

 the inner margin of the oral aperture, as well as the oesophagus, is provided with them. 

 A short ciliated oesophagus is present. As stated previously, Fouquet and Zacharias 

 believe that this oral aperture acts as a sucker rather than as a mouth. While not 

 denying the possibility of its acting as a sucker, although I have seen no proof for the 

 view, I see no reason for denying that food can enter the body through this opening. 

 The oral and oesophageal cilia certainly would be of more use in forwarding food 

 than in sucking fast to an object, yet at the same time I have not seen any food enter 

 through this aperture, nor, as I intimated above, have I seen it act as a sucker. No 

 anus was discovered, neither could I confirm Kerbert's statement that the fieces were 

 expelled from various points on the surface; I was also unable to discover any tri- 

 chocysts. 



The entire body, with the exception of a narrow zone immediately surrounding the 

 oral aperture, is covered with short cilia arranged regularly in rows. 



The protoplasm of the body is indistinctly divided into an endoplasm and an 

 ectoplasm. In the ectoplasm are found numerous globules, such as have been described 

 by former authors, and numerous contractile vacuoles. The latter are arranged, appar- 

 ently in no regular order, throughout the entire ectoplasm, but each vacuole seems to 

 be a more or less permanent structure, i. e., as soon as a vacuole has emptied itself to 

 the exterior through a minute but perfectly visible canal it appears again at the same 

 point. Following one vacuole under the microscope for some time I found that it 

 contracted on an average every 7 seconds. 



The endoplasm contains very numerous globules and a cresceutic nucleus, both of 

 which have been sufficiently described by former authors. 



*This apparent change in the position of the month is, of course, nothing more nor less than a 

 general change in orientation of the entire body. 



