10 



THE HYDROMEDUSAE 



FlO. 14. 



Fio. 15. 



11. Ocellus of Lizeia Koettikeri. oc, pigmented ectxxiermal cells ; I, lens. 



12. Otocyst of Phialidium. d l , superficial layer of ectoderm ; <&, deep layer of ecto- 

 derm ; ft, auditory cells of ectoderm ; hh, auditory hairs ; np, nerve body ; TIT-I, upper nerve 

 ring ; r, endoderm cells of the circular canal. The otolith cavity is seen above h. (Figs. 

 11, 12, from Lankester, after Hertwig.) 



13. Otocyst of Euchilota. o, otolith ; remaining letters as Fig. 12. (After Hertwig.) 



14. Simple tentaculocyst of one of the Trachomedusae (Khopalonema velatum). The process 

 carrying the otolith or concretion hk, fonned by endodenn cells, is enclosed by an upgrowth 

 forming the " vesicle," which is not yet quite closed in. (From Lankester, after Hertwig.) 



15. Optical section of a cordylus or sense club ; the surrounding structures are only 

 roughly indicated. CC, circular canal; EU, exumbral surface; Me, mesogloea; NR, the 

 outer, NR, the inner parts of the nerve ring; SU, subumbral surface; T, tentacle; V, 

 velum. (After Brooks.) 



