386 APPENDIX. 



sexual generation, vol. i. p. 192), from adhering hydroid polyjjs 

 (2, 3). These latter, however, originate out of the fructified eggs 

 of the medusae (therefore by sexual generation, vol. i. p. 195). 

 Hence the non-sexual, adhering generation of polyps (I., III., 

 v., etc.) regularly alternates with the sexual, freely swimming- 

 generation of medusse (II., IV., VI., etc.) This alteration of 

 generation can only be explained by the Theory of Descent. 



The same remark applies to a kindred form of propagation, 

 which is still more remarkable, and which I discovered in 1864, 

 -near Nice, in the Elephant- jellies (Geryonida), and called allcp.o- 

 gony, or alloeogenesis. In this case two completely distinct forms 

 of medusa are descended from one another ; the larger and more 

 highly developed generation (11), Geryonia, or Carmarina, is six- 

 rayed, with six foliated sexual organs, and six very movable 

 marginal filaments. From the centre of its bell-shaped cup, like 

 the tongue of a bell, hangs a long proboscis, at the end of which 

 is the opening of the mouth and stomach. In the cavity of the 

 stomach is a long, tongue-shaped bunch of buds (which on 

 Plate VII. (n) is extended from the mouth on the left like a 

 tongue). On this tongue, when the Geryonia is sexually ripe, 

 there bud a number of small medusse. They are, however, not 

 Geryonise, but belong to an entirely distinct but very different 

 form of medusa, namely, to the genus Cunina, of the family of 

 the ^ginida. This Cunina (12) is very differently constructed ; 

 it has a flat, semi-globular cup without proboscis, consists in 

 early life of six divisions, later of sixteen, and has sixteen bag- 

 shaped sexual organs, and sixteen short, stiff, and strongly curved 

 tentacles. A further explanation of this wonderful alloeogenesis 

 may be found in my " Contributions to the Natural History of 

 the Hydromedusse." (Leipzig, Englemann, 1865), the first part 

 of which contaias a monograph of the Elephant-jelUes, or 

 Geryonida, illustrated by six copper-plates. 



Even more interesting and instructive than these remark- 

 able relations are the vital phenomena of the Svphonophora, 

 whose wonderful polymorphism I have frequently spoken of, 

 and described in a popular manner in my lecture on " Differentia- 



