PLATE IX. 



Tlie lettering is the same in all the figures. 



o Acontia. 



b Mesenteric filaments. 



c Stomata in the supta. 

 c ' Perioral stomata. 

 c" Marginal stomata. 

 cu Cuticle. 



d Glandular streaks of the mesen- 

 teric filaments. 



e Ciliated streaks of tlie mesenteric 

 filaments. 

 ek Ectodemi. 

 en Kndoilerm. 



y Keproductive organs. 



h Septa, rh Directive septa. 



i OxaX disk. 



k Wall. 

 I Pedal disk. 

 m Muscles. 

 inm Mesodermal muscles. 

 ml Longitudinal muscles of the septa. 

 mP Retractor. 

 mp Parietobasilar muscle. 

 mt Transverse muscles. 

 mr Radial muscles of the oral disk 

 aud longitudinal muscles of the 

 tentacles 

 ms Circular muscle of the wall. 

 me Mesoderm. 

 n Urticating cells. 

 Ovicells. 



I> Filamental apparatus of the ovicells. 

 ]>^ Process of the ovicell. 

 p- A[jical set of epithelial cells. 

 r Marginal spherules. 

 rh Directive septa, 

 s CEsophagus. 

 so Openings of the oisophagus into 



the radial chambers. 

 «• (Esophageal grooves. 

 la Lappets of the lesophagus. 

 t Tentacles and the openings homolo- 

 gous with them. 

 t ' Principal tentacles. 

 t'^ Acces.sory tentacles. 

 V Openings of the pedal disk. 



All statements given as to magnifying powers have reference to Zeiss's system. The magnifying powers amount to 



A 

 C 



D 

 F 

 J 



A with uns.'rcwed front lens (.unscr. A) magnifies with Oc. 1 : -50 times; with Oc. 2 : 40 times. 



Polysiphonia tuherosa (figs. 1-10). 



Fig. 1. Transverse, section through the pedal disk, showing the muscular fibres which 

 pass on to the furrows. A, Oc. 2. 



Fiff. 2. Transverse section throuoh a tentacle bulb. a\ Oc. 1. 



Fig. 3. Horizontal section through the pedal disk. The upper part of the diagram is 

 near the outer surface ; the lower shows the section passing transversely through the 

 bases of two septa. A, Oc. 2. 



Fig. 4. Radial section through the pedal disk. C, Oc. 2. 



Fig. 5. Pedal disk, natural size, seen from the lower side ; about one-sixth of it shown. 



Fig. 6. Transverse section through the tentacle near the point, a^, Oc. 1. 



Fig. 7. Part of a transverse section through the pedal disk (fig. 1) more highly 

 mamified. C, Oc. 2. 



Fig. 8. Tentacles seen from the side ; natural size. 



Fig. 9. A tentacle divided longitudinally ; natural size. 



Fig. 10. Bottom of a, radial furrow of the pedal disk, with the adjacent muscular 

 fibres ; seen in transverse section. C, Oc. 1. 



Corallimo7-2)huii rigidus (figs. 11 aud 12). 



Figs. 11 and 12. Transverse sections through the wall. 



