a Aeontia. 



i mesenteric filaments. 



c Stomata in tho septa. 

 .•' Perioral stomata. 

 c- Marginal stomata. 

 eix i uticle. 



d Glandular streaks of the mesen- 

 terie filaments. 



e Ciliated streaks of the mesenteric 

 filaments. 

 ek Ectoderm. 

 i i Kndoderin. 



;/ Reproductive organs. 



A Septa, rh Directive septa. 



i Oral disk. 



PLATE XI. 



The lettering is the same in all the figures. 



k Wall. 

 I Pedal disk. 

 m Muscles. 



mm Mesodermal muscles. 

 ml Longitudinal muscles of the septa. 

 mP Retractor. 

 m/i Parietobasilar muscle. 

 int. Transverse muscles. 

 mr Radial muscles of the oral disk 

 and longitudinal muscles of the 

 tentacles 

 ins Circular muscle of the wall. 

 me Mesoderm. 

 n Urticating cells. 

 o Ovicells. 



/) Filamental apparatus of the ovicells. 

 p 1 Process of the ovicell. 

 ji 2 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. 

 sz Lappets of the oesophagus. 



/, Tentacles and the openings homolo- 

 gous with them. 

 t l Principal tentacles. 

 t' 2 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' 



A 

 C 



D 



F 

 J 



Oc. 1. 

 195 

 410 

 470 



Oc. 2. 

 240 

 550 



580 



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



Pohjopis striata (figs. 1-12). 

 (Figs. 1-8, Unscr. A, Oc. 1.) 



Fig. 1. Transverse section through the oral disk near the stomidia, corresponding to 

 line a in fio;. 6. 



Fig. 2. Transverse section through the oral disk, rather more towards the centre, 

 corresponding to line ft. 



Fig. 3. Transverse section through the oral disk, still more towards the centre, 

 corresponding to line y. 



Fig. 4. Transverse section through the upper part of the oesophagus and the openings 

 lying in it. 



Fig. 5. Transverse section through the oral disk, near the oral opening, corresponding 

 to line e. 



Fig. 6. Surface view of a part of the oral disk. Unscr. A, Oc. 1, and reduced to one- 

 eighth. 



Fig. 7. Transverse section through the oral disk, nearly midway between figs. 3 and 

 5, corresponding to line S. 



Fig. 8. Transverse section through the lower part of two directive septa. 



Fig. 9. Transverse section through a septum and the oral disk in the region of the 

 stomidia. A, Oc. 2. 



Fig. 10. Eadial section through the oral disk, endodermal side. C, Oc. 2. 



Fig. 11. The lower end of the body-wall a seen from the ectodermal side, /3 seen from 

 the gastric side, about twice the natural size. 



Fig. 12. Septum with adjacent portion of the wall, oral disk and oesophagus ; natural 



size. 



Paractis excavata (figs. 13 and 14). 



Fig. 13. Transverse sections through a tentacle, a at the point, b in the middle, c at 

 the base. Unscr. A, Oc. 1. 



Fig. 14. Part of a similar transverse section more highly magnified. D, Oc. 1. 



