No. 6.] THE MORPHOLOGY OF THE ACTINOZOA. 263 



Streak, and to test the accuracy of this appearance I endeav- 

 ored to obtain a longitudinal section 

 of the filament which would cut the 

 epithelium of the median lobe above 

 and the glandular streak below. 

 After many trials I obtained a 

 series, from three successive sec- 

 tions of which it was easy to reconstruct a median 

 section through the filament. Such a reconstruc- 

 tion is represented in Fig. 5, somewhat diagram- 

 matically. 



In Fig. 6 is shown the appearance of a portion 

 of the stomatodaeal ectoderm from the region 

 indicated in Fig. 5 by a. It will be seen from 

 this that the epithelium in this region is high, and 

 that it contains numerous gland cells with clear 

 contents ; gland cells with granular contents are, 

 on the contrary, rather rare. In addition, some 

 darkly staining, slender, probably sensory cells 

 occur, the rest of the tissue being composed of 

 ciliated cells which stain only moderately, and are 

 probably supportive cells. As I have already 

 stated, the median epithelium of the ciliated bands 

 is continuous with this above, and is histologically 



identical with it. Tracing 

 the section downwards, 

 however, it will be found 

 that the median epithelium gradually 

 becomes lower, and, at a certain region, 

 it changes somewhat abruptly its histo- 

 logical character. 



Fig. 7 represents a portion of the 

 epithelium at the region where the 

 change takes place {b in Fig. 5). The 

 upper part of the portion figured is 

 essentially the same as the stomatodaeal 

 ectoderm, but in its lower part there appear cells which stain 

 somewhat darker than the ordinary supporting cells and have 



Fig. 5. — Recon- 

 struction from 

 three sections of 

 a longitudinal sec- 

 tion through the 

 stomatodaeum, 

 the median lobe of 

 the ciliated band 

 and a glandular 

 streak of Z. soci- 

 attis. a-d = the 

 levels from which 

 Figs. 6-9 are 

 taken. 



Fig. 6. — Portion of Fig. 5 about 

 the region marked a, more highly 

 magnified. 



