PLATE XIII. 



The lettering is the same in all the figures. 



a Acontia. 



b Mesenteric filaments. 



c Storaata iu the septa. 

 c' Perioral stomata. 

 c - Marginal stomata. 

 cu, Cuticle. 



d Glandular streaks of the mesen- 

 teric filaments. 



« 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. 

 m Muscles. 

 mm Mesodermal muscles. 

 ml Longitudinal muscles of the septa. 

 mP Retractor. 

 mp Parietobasilar muscle. 

 mt Transverse muscles. 

 mr Radial muscles of the oral disk 

 and longitudinal muscles of the 

 tentacles 

 ms Circular muscle of the wall. 

 me Mesoderm. 

 n Urticating cells. 

 Ovicells. 



p Filamental apparatus of the ovicells. 

 p ' Process of the ovicell. 

 p^ Apical set of epithelial cells, 

 r Marginal spherules. 

 rh Directive septa. 

 ■1 (Esophagus. 

 S'i Openings of the oesophagus into 



the radial chambers. 

 Sf ^Esophageal gi'ooves. 

 sz 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. 



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



Fig. 1. Transverse section tlirough the mesoderm, ectodermal epithelium, and cuticle 

 of Scytojihorus striatus. D, Oc. 2. 



Fig. 2. Longitudinal section through the pleated circular muscles of the wall at the 

 lower end of Halcampa davits. A, Oc. 1. 



Fig. 3. Transverse section through the body of Sci/tojDhonts striatus passing through 

 the cesophagus. a^, Oc. 1. 



Fig. 4. Transverse section through the body of Halcatnpa clavus, passing through the 

 oesophagus, a^, Oc. 1. 



Fig. 5. Section parallel to the surface through the pedal disk of Halcampa clavus. 

 C, Oc. 1. 



Fig. 6. Transverse section through the pedal disk of Halcampa clavus. C, Oc. 1. 



Fig. 7. Half a transverse section through the lower extremity of Halcampa clavus. 

 a\ Oc. 1. 



Fig. 8. Transverse section through the cuticle of Sci/tophorus striatus. D, Oc. 2. 



Fig. 9. Septum of the first order of Aatholoha reticulata; natural size. 



