Explanation of Plate IV. 

 The Corynidce. 



Fig. 1. Syncoryne eximia, natural size of colony. 



Fig. 2. Normal hydranth of same showing developing medusiform 

 persons, mb 1 to m& 5 , in various stages, disposed irregularly 

 between the capitate tentacles ; mb 5 is the oldest and is 

 all but ready to be set free ; pr. perisarc. X 30. 



Fig. 3. A free medusa (Sarsia) of Syncoryne, fully mature (probably 

 two months after being set free) ; m. manubrium, within 

 whose walls sperm has been developed, this individual 

 being a male ; i.e. a captured Copepod being digested 

 within the cavity of the manubrium ; r.c. radial canals ; 

 c.c. circular canal ; e.s. eye-spot or ocellus ; o. mouth ; 

 v. velum ; t. tentacle. X 4|. 



Fig. 4. Hydranth showing abnormal medusiform person, a.m.b., 

 wherein, while the bell is fully developed, the tentacles 

 are aborted, and the manubrium functions solely as a 

 reproductive organ (in this case, a spermarium). The 

 bell remains permanently attached and the reproductive 

 products are ripened in situ ; d.m.b. developing medusa- 

 bud ; e.s. eye-spot ; p. perisarc ; c. ccenosarc ; o. mouth. 



Fig. 5. A row of axial endoderm cells from a tentacle of Syncoryne. 

 x 180. 



Fig. 6. Colony of Coryne vaginata, nat. size. (The annulations 

 of the stem are not visible to the naked eye, in living 

 specimens). 



Fig. 7. Hydranth from a male colony of same species ; m.g. male 

 reproductive capsule, representing a degenerate medusa. 



Fig. 8. Hydranth from a female colony ; f.g. female capsules filled 

 with ova ; t. tentacles ; n. stinging threads of nematocysts ; 

 o. mouth ; c. tiny membraneous cup at the base of the 

 hydranth. X 30. 



Fig. 9. Nematocysts from tentacle of Coryne vaginata, x 600. 



A & C, two burst nematocysts, showing barbs (6.) in different 

 positions ; th. the evaginated threads ; B, an unburst 

 nematocyst, showing the trigger (t), and the coiled thread 

 lying within the cyst (c) ; n. nucleus. 



