PLATE X. 



The lettering is the same in all the figures. 



i icontia. 



b Mesenteric filaments. 



r Stomata in the septa. 



t l Perioral stomata. 



■' Marginal stomata. 

 cm ' 'utiele. 



(I Glandular streaks of the mesen- 

 teric filaments. 



e Ciliated streaks of the mesenteric 

 filaments. 

 ck Ectoderm. 

 en Endoderm. 



g Reproductive organs. 



h Septa. rh Directive septa. 



i Oral disk. 



k Wall. 

 I Pedal disk. 

 m Muscles. 

 7/ini Mesodermal muscles. 

 ml Longitudinal muscles of the septa. 

 ml 1 Retractor. 

 mp Parietobasilar muscle. 

 ml Transverse muscles. 

 mr Radial muscles of the oral disk 

 and longitudinal muscles of the 

 tentacles 

 ins Circular muscle of the wall. 

 mc Mesoderm. 

 n Urticating cells. 

 o Ovicells. 



p Filamental apparatus of the ovicells. 

 p 1 Process of the ovicell. 

 p 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. 

 t Tentacles and the openings homolo- 

 gous with them. 

 I ' 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 



Oc. 1. 



a' 6 



A 5o 



C 95 



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



1 : 30 times ; with Oc. 2 : 40 times. 



Oplilodiscus annulatus (figs. 1-10). 



Fig. 1. A portion of the animal, seen from the side ; magnified a little. 



Fig. 2. Transverse section through a tentacle near the base. Unscr. A, Oc. 2. 



Fig. 3. A portion of the animal seen from the oral side ; natural size. 



Fig. 4. A principal septum with the two adjoining genital septa; magnified a little. 



Fig. 5. Transverse section through the oral disk at the insertion of a septum. A, 



( )r. 2. 



Fig. 6. Transverse sections through different parts of the circular muscle : a through 

 the upper part, 8 through the lower end. Unscr. A, Oc. 2. 



Fig. 7. Portions of the circular muscle, more highly magnified ; a from the upper, /3 

 from the lower end. D, Oc. 2. 



Fig. 8. Pseudo-tentacle, slightly magnified. 



Fig. 9. Some terminal branches of the pseudo-tentacle, ten times the natural size. 



Fig. 10. Longitudinal section through a branch of the pseudo-tentacle. J, Oc. 1 ; 

 and reduced one half. 



Antholoba reticulata (figs. 11 and 12). 



Fig. 11. Transverse section through the circular muscle. D, Oc. 2. 

 Fi«\ 12. Transverse section through the oral disk. C, Oc. 1. 



