JELLY-POLYPS 35* 



nectophore and jelly-polyp is less well-developed, and their endodermal canals are relatively larger 

 in diameter and still open. PI. XXI, fig. 4 shows the last four dichotomies of part of an immature 

 gonodendron spread out on a microscope slide. 



B 



sub-term — 



D 



pro-bud 1 

 B1 



pro-bud A\ 

 (palpon) 



A 2 1B A 2 1A 



sub-term 

 erm | Jerm 



jelly-polyp 



palpon 



term 1 ^^,'c"" 



sub-term 



sub-term 

 term 



Text-fig. 27. Physalia physalis. Early growth stages (hypothetical) of branches of a gonodendron. A later growth stage of 

 fig. F{d. PI. XXII, fig. 2) is shown in PI. XXII, fig. 5. sub-term = sub-terminal section, term = terminal section, 1, 2, 3 etc. 

 = successive dichotomies, A x , A 2 , AJ, A 2 1A , etc. = successive buddings. 



Jelly-polyps 

 (PI. XXI) 

 As stated on page 348 there is at the base of each terminal branchlet a palpon which has at its base a 

 jelly-polyp. These are well shown in PL XXI, figs. 1, 2, 6, 7. It is necessary to understand the regular 

 type of branching just described in the gonodendra in order to demonstrate that the jelly-polyps are not 

 vestigial stalks left after the nectophores have dropped off, an erroneous interpretation put forward by 

 Huxley, Haeckel and Chun. 



In the older growth-stages, both jelly-polyp and nectophore-stalk look much alike (PI. XXI, fig. 3). 

 This resemblance of the oldest known growth-stage of these two buds is due to the fact that in each 

 the endodermal lumen becomes relatively reduced at the same time as the mesogloea becomes very 

 much thicker (PI. XXI, fig. 3). In both cases the endodermal canal — now almost occluded — comes to 

 lie on the abaxial side, next to the ectodermal fold (PL XXI, fig. 6) except sub-terminally, where it lies 

 centrally to link up with the sub-umbrella of the nectophore and the tip of the jelly-polyp. This 

 structural resemblance between the basal parts of these two kinds of buds — one a medusoid and the 

 other, once thought to be a polyp, but now shown to be a reduced nectophore— was for long inex- 



7-2 



