THE HYDROMEDUSAE 



cnidoblasts. On the outer edge of the bell are also found in some 



Fio. 32. 



Fio. 30. 



Fio. 34. 



FIG. 33. 



30. Small portion of a hydrocladium of a Plumularian hydroid. Between two annulations- 

 of the hydrocladium lie (n) a hydroid projecting from its hydrotheca ; (b) above it two 

 lateral nematophores (modified hydroids), one of which is expanded ; (c) below it a single 

 median nematophore, also expanded, and spreading over the hydrotheca. (After Allman.) 



31. Perisarc of a small portion of a hydrocladium of Aglaophenia Jtticulct, viewed at right 

 angles to the plane of Fig. 30, showing between each two annulations of the hydrocladium, one 

 hydrotheca, two lateral and one median semitubular thecae for nematophores. (After Allman.> 



32. Diagram of the flattened medusoid of Obelia, showing two of the four perradial canals 

 with the pendent gonads, four of the eight adradial otocysts. 



33. View of the oral surface of one of the Leptpmedusae (Irene pellucida, Haeckel), to 

 show the numerous tentacles and the otocysts. ge, genital glands ; M, manubrium ; ot, otocysts ; 

 re, the four radiating canals ; Ve, the velum. (From Lankester.) 



34. Part of the edge of the bell of a Leptomedusan. CC, circular canal ; MC, marginal 

 cirrhus ; MF, marginal funnel ; .1/7', marginal tubercle ; RC, opening of radial into circular 

 canal ; T, tentacle (cut short) ; V, velum. (Modified from Haeckel.) 



genera marginal tubercles, slight prominences on the body wall, 

 generally containing a prolongation of the coelenteron, often 



16 



