No. 3.] MORPHOLOGY OF THE STENTORS. 489 



"hypostom" is based upon the wrong assumption that the 

 mouth is at the entrance of the funnel, it is desirable to give 

 this structure a new designation, and I propose the term 

 "velum" (Figs. I, 33, vel). The velum is covered outwardly 

 by the pellicula of the anterior portion of the body and inter- 

 nally by that lining the buccal pouch. It is probable that the 

 ectoplasmic layers of the two surfaces are in contact, but 

 when contraction takes place the endoplasm flows in between 

 the surfaces, and the velum is almost or even wholly obliter- 

 ated. 



The descent from the higher and more aboral portion of the 

 frontal field into the buccal pouch is very sharp and sudden. 

 At the left the pouch curves dorsalwards and forms a pocket 

 which is partially covered by a reduplicature of the frontal 

 field — the "buccal fold" (Fig. I, b.f), — and by the adoral 

 zone. This is the beginning of the "Rinne " of Schuberg ('90, 

 p. 203), which he figures as a channel starting from this point 

 and traversing the ventral side of the pouch towards the mouth. 

 This channel, however, is almost entirely obliterated in the 

 fully-expanded condition of the buccal pouch. At its right 

 extremity the pouch narrows suddenly, and passes inward and 

 dorsalward to form the inner turn of the pharyngeal spiral, 

 or pharynx proper (Fig. I, //^.). 



The foregoing description of buccal parts applies particularly 

 to the Blue Stentor. These parts are, however, almost equally 

 well-developed in 6". roeselii and vS. polymorpJuis ; in both 

 species the buccal pouch is especially prominent. In the lowly- 

 organized forms, such as .S". igneiis and 6". pyriforniis, no buccal 

 pouch is present. (Figs, i, 2.) Allied genera, as Climacosto- 

 mum and Folliculina, also appear to be destitute of a buccal 

 pouch, so that this structure may fairly be considered as 

 developed among the Stentors, and only in the higher species 

 of the group. 



4. Endoplasmic Stj'iictures . 



MembranellcB. — It was first pointed out by Sterki ('78) that 

 the adoral zone of the Heterotricha (Stentor) and Hypotricha 

 is composed, not of large cilia as held by Stein ('67) and Simroth 



