Characteristics of Rotifers. 293 



contact with the jaws, which for any reason are not acceptable, 

 they are thrown up through the buccal funnel by a peculiar 

 scoop -like action of the unci, which is very curious to 

 witness/' 



A simplification of this description will obviously apply to 

 Notommata clavulata, and to the jaws of the Asplanchna 

 Frightwellii, shown in the plate ; but it should be remarked 

 that Mr. Grosse shows how strongly the jaws of the Asplanchna 

 resemble the incus portion of the more complicated jaws of 

 Synchwia tremula and Diglena forcipata, the mallei in 

 Asplanchna being scarcely visible, and possessing no important 

 function. Mr. Gosse's paper must be consulted to understand 

 how the various parts are modified, or become obsolete in 

 different genera; but it is advisable here to cite his popular 

 explanation of the state of the organ in the common rotifer. 

 He says, " Suppose an apple to be divided longitudinally, 

 having the stalk attached to one half. Let this now be split 

 longitudinally, so far as the stalk, but not actually separating 

 any portion from it. Draw the two portions apart, and lay 

 them down on their rounded surfaces. They now represent 

 the quadrantic masses [composed of soldering together the 

 'mallei and incus~\ , the stalk being the fulcrum, and the upper 

 surfaces being crossed by the teeth. By the contraction of 

 the muscles of which they are composed, the two segments 

 are made to turn on their long axes until the points of the teeth 

 are brought into contact, and the toothed surfaces rise and 

 approach each other.-''' 



In the Floscules, Mr. Gosse finds the mastax, or bulb, 

 wanting, " the dental apparatus, which is very small, 

 springing from the paries (wall) of the stomach just below 

 the second diaphragm.'" 



The preceding quotations will serve as an introduction to 

 the study of this, the so-called gizzard of rotifers ; but it is 

 important to state in connection with Mr. Gosse's opinion, 

 that these organs are jaws, that he has witnessed their pro- 

 trusion in Furcularia, Pleurotrocha, Taphrocampa, Notommata 

 clavulata, N. aurita, N. petromyzon, JV. parasitica, Flagio- 

 gnatha, Scaridium, Synchceta, Folyarthra, Diglena, Asplanchna, 

 Hastigocerca, Monocerca, Salpina, Monostyla, and Anurcea. As 

 some of these are common species, Mr. Gosse's statements are 

 easily verified by any student. 



The stomachs and intestines of rotifers are richly ciliated, 

 and near the stomachs may usually be seen bodies of consider- 

 able size, which appear to be organs secreting some fluid 

 necessary to the process of digestion. In Asplanchna, the very 

 curious circumstance occurs of a creature so highly organized 

 being destitute of an intestine, or an anal orifice. The undigested 

 portions of its food being cast out through the gullet and 



