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JOHNSON. [Vol. VI 1 1. 



(•76), but of flat, transverse plates, called by Sterki "membra- 

 nellse." His observations have been confirmed by all subsequent 

 writers upon these structures. Schuberg's careful description 

 of the membranella2 of S. ccsrtdeus relieves me from giving a 

 detailed account of them. I have studied them as independ- 

 ently as I could, and my results agree with his at almost every 

 point. 



When the membranellae are in rapid motion the impression 

 is that of large, strong cilia, each inserted at the lower 

 extremity of a glistening rod extending across the adoral 

 zone. The same appearance is very strong when the mem- 

 branell^ are moving slowly, and after a few observations of this 

 sort it is almost impossible to avoid forming the conclusion that 

 one has to do with large cilia. But in order to obtain a true 

 conception of them, their motion must be arrested and a side- 

 view obtained. By bringing sufficient cover-glass pressure 

 upon the adoral zone, the membranellae are flattened down 

 and made to overlap one another, all motion being reduced 

 to a slight tremor (Fig. 6, m). Then the whole outline is 

 seen. 



After fixine; with corrosive sublimate or other suitable re- 

 agent, the membranellae may be studied either in optical 

 section or actual ones, and both extra- and intrapellicular 

 portions of the membranellae may then be observed. (Figs. 

 8, m. and 13, a.z.^) In side view, as in Fig. 8 (where the 

 section cuts the newly-formed adoral zone transversely) the 

 basal plate {b.p.m.) and its terminal filament (//.) are plainly 

 seen. When the zone is examined in longitudinal optical 

 section (Fig. 1 3), a third intrapellicular structure is visible, the 

 connecting filament {c.f), — the " Basalfibrille " of Schuberg. 

 By focusing through the adoral zone, this fibre is also seen in 

 the living animal. Another structure plainly seen, is the 

 thickened and highly-refractive basal portion (" Basalsaum " of 

 Schuberg i*). Figs. 13, 30, just outside the pellicula. This I 

 regard as homologous with the "basal piece" (Fussstuck) of a 

 cilium, and has in young membranellae precisely the same 

 appearance as in cilia. Although I have not traced it through- 

 out the development of the membranellae, there can be little 



