PLATE XXV 



Fig. i. Part of a small tentacle from a basal branch of cormidium II 

 of specimen Lanzarote, no. 2, to show the longitudinal muscular 

 lamella and nematocyst heads, each containing about 600 nemato- 

 cysts (0-027 mm - or Tooo mcn m diameter), x 30. 



Figs. 2 and 3. Palpons of a specimen from Chesil Beach, Dorset, B.M. 

 Register no. 1954. 10.9. 1, to show apical opening of palponsi 

 analogous to an anus. Fig. 2 x 29, fig. 3 x 25. 



Fig. 4. Living and still reactive tentacular nematocysts of Physalia (by 

 courtesy of Dr Charles E. Lane, University of Miami). The two 

 size groups average 11-5/* and 26-8 fi in diameter. Optical sections 

 of the coiled-up threads show that the threads taper towards the 

 tip (anisorhizas). The point of emergence (P) to which the base of 

 the thread is attached is indicated in this photograph by a dark 

 prominence, x 1500. 



Fig. 5. Oral end of a gastrozooid to show apical pads of nematocysts 

 and meridional striae. Both of these features are absent in the 

 palpons. x 32. 



