PLATE XL 



The lettorin'' is the same in all the figures. 



a Acontia. 



6 Mesenteric filaments. 



c Stoniata in the .septa. 

 c'- Perioral stomata. 

 c'^ Miir^inal stomata. 

 ca Cutiele. 



d Glandular streaks of the mesen- 

 terie, lilaments. 



e Ciliated streaks of the mescnterie 

 filaments. 

 ek Ectoderm. 

 en Endoderm. 



fjr Reproductive organs. 



h Se])ta. rh Directive septa. 



i Oral disk. 



k ■Wall. 

 I Pedal disk. 

 m Muscles. 

 Mill Mesodermal muscles. 

 ml Lon,L;itU(Uual muscles of the septa. 

 7nP Ketrautor. 

 mp Parietobasilar muscle. 

 'int Transverse muscles. 

 mr Radial muscles of the oral disk 

 and longitudinal muscles of the 

 tentacles 

 ms Circular muscle of the wall. 

 me Mesoderm. 

 71 Urticating cells. 

 Ovicells. 



p Filamentalapparatng of the ovicells. 

 7; ' Process of the ovicell. 

 p^ Apical set of epithelial cells, 

 r Marginal spherules. 

 rh Directive septa. 

 s QJsophagus. 

 so Openings of the oesophagus into 



the radial chambers, 

 sr Oesophageal grooves. 

 sz Lappets of the ccsophagus. 

 t Tentacles and the openings homolo- 

 gous with them. 

 1 1 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 



Oc. 1. Oc. 2. 



a' 6 10 D ... 



A 55 70 ¥ ... 



C 95 125 J ... 



A with unscrewed front lens (unscr. A) magnifies with Oc. 1 



Oc. 1. Oc. 2. 



195 240 



410 550 



470 580 



: 30 times ; with Oc. 2 : 40 times. 



Poli/ojyis striata (figs. 1-12). 

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



Fio-. 1. Transverse section tlirougli the oral disk near the stomidia, corresponding to 

 line a in fig. 6. 



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

 corresponding to line ^. 



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 8. 



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. Radial 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, /8 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, h 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. 



