62 



ried out with the ectoderm as it becomes applied to the 

 tentacle-base. But al'ter a certain time the tentacle in- 

 creases only very slowly in length and additional nettling 

 cells are needed to keep up with the inci'ease in diameter. 

 This migration of nematocysts has been seen and described 

 by Hurbach in his paper on the nettling organs in Hydroids 

 (Arch. f. Naturg. 1894 ). After the capsules have become 

 established, the ectodermal covering becomes modified to 

 form the cnidocil (Fig. 32, en.). The nerve connection is 

 developed at an early stage. 



XIV . SEXU AL ORGANS . - 



In minute specimens of the adult gonosome the 

 gonads t.re frequently found in their first stage of devel- 

 opment. They appear as outgrowths of the ectodermal cover- 

 ing of the radial canals, at first in the for-m of rounded 

 lumps projecting downwards from the radial canal into the 

 subumbrella at a point two-fifths of the distance from the 

 top of the bell to the margin. The rudimentary lump of go- 

 nadial tissue elongates in both directions from the point 

 at which it started. (Text-figure B shows the condition in 

 Olindias , where it is identical at first with that in Go- 



