poeter: teichonympha. 53 



margin rests ou the anterior sloping sui'face of the outer layer (st.'"), 

 while the anterior end of the inner la\'er (stj) is covered by the expanded 

 knob-like portion (tub.) of tlie protoplasmic core (Figs. 7 and 8). 



The whole of this portion, forming the nipple-like projection of the 

 anterior extremity of the animal, is veiy active in the living creature; 

 it is constantly in motion, turning from side to side, and, as it were, 

 nosing its way through tlie crowd of its associates. 



The axial rod (Figs. 7, 8, ax.) is apparently the only means of union 

 between this nipple-like part of the animal and the bell-shaped region, 

 for a fissure (Figs. 7, 8, jis.), encircling the base of the nipple, penetrates 

 the layers surrounding the axis, thus severing all other connection. 

 Behind the fissure, what seem to be continuations of the outer and 

 inner layers of the nipple are can-ied backward over the bell-shaped 

 region, i. e. over a little less than one third the length of the animal. 

 A middle layer never appeal's in this region, a fact which makes it seem 

 probable that such an appearance in the nipple region is due merely to 

 a space between the inner and outer layers. Since the enveloping layers 

 are so much alike in the nipple- and bell-shaped regions, I shall not 

 attempt to give a separate description of them in each region, but pro- 

 ceed at once to state what I have to say about these layers for the 

 whole "head" region. 



The inner layer stains only slightly, if at all. From the fissure back- 

 wards, as far as it extends, it is marked by fine lines perpendicular to 

 the surface. This appearance is due to the cilia, which penetrate both 

 the enveloping layers. The same structural condition probably exists 

 in front of the fissure, although it was not possible, owing to the small 

 diameter of the nipple-like projection (about 6 fi) and the thickness of 

 my sections (3.3 /u), to detect any striations. 



The cilia arise from the granular protoplasm, at the deep surface of 

 the inner layer, which they traverse, and thus give a striated appear- 

 ance (Fig. 16, st.str.). They are of about the same refractive power 

 and stainability as the outer layer, and consequently I have not been 

 able to trace them through that layer; but I think that their passing 

 through it is hardly questionable. The arrangement of the radial stria- 

 tions of the inner layer, which 1 believe to be due to the cilia, is best made 

 out from tangential sections of the bell, where their cut ends appear as 

 dots. The dots are placed in quincunx order, much as shown in Fig. 

 20. This arrangement gives two series of diagonal rows of dots cross- 

 ing each other nearly at right angles and making angles of 45 de- 

 gi-ees with the longitudinal axis of the auiiuul. Secondary rows, both 



