A NEW GENUS OF OLIGOOH^TA. 473 



(13), Horst (12), and Rosa (10). As the latter has pointed 

 out, Perrier appears to have described a specimen in which the 

 buccal cavity was partly everted ; while Horst, in statiug that 

 the mucous gland opened on to the first segment of the body, 

 was deceived by the introversion of the peristomial segment. 



Among the half-dozen series of longitudinal sections of 

 Urochseta corethrura which I possess there is one in which 

 the 1st and a portion of the 3nd segment are introverted, 

 and the mucous gland appears, therefore, to open into the 

 buccal cavity; in fact, it actually does open into a temporary 

 extension of the buccal cavity. 



It is, in my opinion, possible to believe that a temporary 

 introversion, such as that to which I havejust referred, 

 may become permanent. In this case what will happen 

 are two events of importance. In the first place the body will 

 be shortened by one segment ; in the second place the '' mucous 

 gland " will come to open into the anterior section of the 

 alimentary tract. 



As to the second point, I may call attention to the remark- 

 able condition of the anterior nephridia in Acanthodrilus 

 multiporus (4). In that worm the anterior segments are 

 occupied by a mass of glandular tubes, clearly of nephridial 

 nature, on each side of the pharynx. Each mass communicates 

 with a long duct, which opens into the buccal cavity. It 

 seems impossible to doubt that the nephridial masses of this 

 Acanthodrilus originally opened on to the exterior, and that 

 their connection with the buccal cavity is only secondary. That 

 this '^ secondary^' connection may be really the original point 

 of opening, masked by the partial or entire introversion of the 

 1st segment, is surely not incredible. 



With regard to the first point, the possible shortening of the 

 body in this way involves really no serious difficulty, though it 

 seems, of course, rather ridiculous to gravely assert that a worm 

 becomes shorter by swallowing its own head. The structure of 

 the epidermis of the 1st segment is more like that of the buccal 

 cavity than it is like that of the succeeding segments. 



These remarks, however, apply more particularly to such 



