PLATE V. 



The lottei'in'' is tliG same in .ill tlie li;;iires. 



n Acontia. 



b Mesenteric filaments. 



c Stomativ in the septiu 

 c ' Perioral stoinata. 

 c- Marginal stoniata. 

 ai Cutielu. 



d Glaiiilular streaks of tlio meaflii- 

 teric lilaments. 



e Ciliateil streaks of the mesenteric 

 filaments. 

 ek Ectoilerm. 

 oi Entloilerm. 



y Reproductive organs. 



h Septa, rh Directive .septa. 



i Oral disk. 



k Wall. 

 / Pedal disk. 

 »i JIusclos. 

 inm Mesodermal muscles. 

 ■ml Longitudinal muscles of the septa. 

 mP Retractor. 

 nip Parietobasilar muscle. 

 mt Transverse muscles. 

 7>ir Radial muscles of the oral disk 

 and longitudinal muscles of the 

 tentacles 

 ms Circular muscle of the wall. 

 mc Mesoderm. 

 n Urticating cells. 

 Ovicells. 



;> Filamental apparatus of the ovicells. 

 p ' Process of the ovicell. 

 p^ Apical set of epithelial cells. 

 )■ Marginal spherules. 

 rh Directive septa, 

 s (Esophagus. 

 so Openings of the oesophagus into 



the radial chambers. 

 sr (Esophageal grooves. 

 sz Lappets of the assophagus. 

 I Tentacles and the openings homolo- 

 gous with them. 

 t ' Principal tentacles. 

 t ^ Accessory tentacles. 

 ■11 Openings of the pedal ili.sk. 



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



A 



c 



Oc. 1. 

 6 

 . 55 



, 95 



Oc. 2. 



ID 



70 

 1'25 



n 



F 



J 



Oc. 1. 



195 

 410 

 470 



Oc. 2. 

 240 

 550 



5iO 



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



Fig- 

 Fig. 



course. 



Polystomidium patens. 



Fig. 1. The portion of the oesophagus, contiguous to the labial margin, with the 

 openings leading into the radial chambers ; three times the natural size. 



Fig. 2. Septum with pedal disk, wall, oral disk, oesophagus, and mesenteric filament ; 

 natural size. 



Fig. 3. Half of the animal seen from the aboral side ; natural size. 



4. Transverse section through the oral disk, near the oral margin. C, Oc. 2. 



5. Transverse section through a mesenteric filament in the upper part of its 

 C, Oc. 1. 



Fig. 6. The entire animal, seen from the oral side ; natural size. As the only 

 specimen sent for examination was greatly injured, some restoration has been necessary. 



Fig. 7. Transverse section through the oral disk, near the stomidia. C, Oc. 2. 



Fig. 8. Longitudinal section through the upper end of the wall, the circular muscle 

 running in it and a marginal spherule. Unscr. A, Oc. 2. 



Fig. 9. Longitudinal section through the circular muscle. D, Oc. 2. 



Fig. 10. Longitudinal section through the lower end of the wall. A, Oc. 2. 



Fig. 11. Horizontal section through the circular muscle. A, Oc. 2. 



Fig. 12. Transverse section through a septum. Unscr. A, Oc. 2. 



