PLATE IX. 



The lettering is the same in all the figures. 



a Acontia. 



b Mesenteric filaments. 



c Stomata in the septa. 

 c ' Perioral stomata. 

 c * Marginal stomata. 

 cu Cuticle. 



d Glandular streaks of the mesen- 

 teric filaments. 



e Ciliated streaks of the mesenteric 

 filaments. 

 ek Ectoderm. 

 en Endoderm. 



g Reproductive organs. 



h Septa, rh Directive septa. 



i Oral disk. 



k Wall. 

 I Pedal disk. 

 in Muscles. 

 mm Mesodermal muscles. 

 ml Longitudinal muscles of the septa. 

 ml 1 Retractor. 

 mp Parietobasilar muscle. 

 nit Transverse muscles. 

 mr Radial muscles of the oral disk 

 and longitudinal muscles of the 

 tentacles 

 ins Circular muscle of the wall. 

 me Mesoderm. 

 11 Urtieatiug cells. 

 o Ovicells. 



p Filamental apparatus of the ovicells. 

 p l Process of the ovicelL 



p- Apical set of epithelial cells. 

 r Marginal spherules. 

 rh Directive septa. 

 s (Esophagus. 

 so Openings of the oesophagus into 



the radial chambers. 

 sr (Esophageal grooves. 

 9z Lappets of the oesophagus. 

 t Tentacles and the openings homolo- 

 gous with them. 

 t ' Principal tentacles. 

 t- Accessory 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 



Oc. 1. 



6 



55 



95 



Oc. 2. 



10 



70 



125 



D 



F 

 J 



Oc. 1. 



195 

 410 

 470 



Oc. 2. 

 240 

 550 

 530 



A with unscrewed front lens (.unscr. A) magnifies with Oc. 1 : 30 times ; with Oc. 2 : 40 times. 



Polysiphonia tuberosa (figs. 1-10). 



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

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



Fiii. 2. Transverse section through a tentacle bulb, a 1 , 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 1 , Oc. 1. 



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

 magnified. 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. 



Corallirnorjphus rigidus (figs. 11 and 12). 

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



