PLATE XXI 



Fig. i. End branchlets of an immature gonodendron to show the 

 pattern of arrangement and the open endodermal canals in the 

 stalks of the nectophores. x 5. 



Fig. 2. One end-branchlet of an immature gonodendron, enlarged, 

 x 87. 



Fig. 3. Part of a gonodendron to show a fully developed end-branchlet 

 consisting of a terminal section (jelly-polyp and terminal palpon) 

 and a sub-terminal section (nectophore and palpon). Several 

 female gonophores are visible. The endodermal canal of the necto- 

 phore is now occluded and the mesogloea hypertrophied both in 

 the nectophore and jelly-polyp, p.st = sub-terminal palpon, 

 n = nectophore, p.t = terminal palpon, jp = jelly-polyp, x 7. 



Fig. 4. Part of an immature gonodendron of a female specimen from 

 the Scilly Isles, kept for a time in a tank in the Laboratory, 

 Plymouth, in November 1954. There are two end-branchlets lying 

 partly on top of each other, so that the jelly-polyp of the right-hand 

 branchlet is almost hidden by the shorter, central palpon. The 

 proximal gonophores are more fully developed than the distal ones. 

 The lumen of the endodermal canal of the stalk of the nectophore 

 is still open, x 16. 



Fig. 5. An end-branchlet of a gonodendron in a middle stage of de- 

 velopment. The jelly-polyp is seen as a hollow, finger-shaped 

 process next to the palpon of the terminal section. At this stage of 

 development the endodermal canal of the stalk of the nectophore 

 is wide open, x 31. 



Fig. 6. Part of a branchlet of an immature gonodendron which has lost 

 the sub-terminal palpon and most of the gonophores. Jelly-polyp 

 on the left, terminal palpon at the bottom, nectophore and gono- 

 phore. The radial and circular canals of the nectophore can be 

 seen in optical section, and also the muscular lamella on the stalk 

 of the nectophore. x 25. 



Fig. 7. The Plymouth specimen (see fig. 4), showing a pair of end- 

 branchlets of a maturing gonodendron. That on the right differs 

 rom the usual type (on the left) in having two terminal sections 

 nstead of one terminal and a sub-terminal section, and so in being 

 vithout a nectophore. Each section on the right has a jelly-polyp, 

 erminal palpon and gonophores. x 10-3. 



