416 W. K. BROOKS ON THE LIFE-HISTORY 



resemblance between them and the medusa-buds, which are produced by many species 

 in exactly the same situation. He therefore advances the hypothesis that the sexual 

 pouches of Agalma arc not organs but buds, which instead of becoming free sexual me- 

 dusas remain in a rudimentary or arrested condition; and, like the degraded medusa- 

 buds of Hydractinia, give rise to ova or spermatozoa. He says "our sexual organs are 

 therefore to be regarded as sexual animals, which, remaining sessile, form with the 

 mother a polymorphic colony. The relation between these appendages and the medusa 

 which carries them is in this species at bottom an alternation of generations." He is 

 careful to state that he does not offer this as an interpretation of the reproductive organs 

 of other species, and he says that while he is not prepared to decide whether the repro- 

 ductive organs of Agalma are homologous with those of other medusae, he inclines to 

 the view that they are not. 



Three years later Allman (3) advanced almost the same hypothesis, but in the form 

 which he [gives to it, the reproductive organs of Agalma and those of all the Antho- 

 medusse are simply organs, while the reproductive bodies of the Leptomedusse are not or- 

 gans but persons. 



The fact that Leuekart first advanced the hypothesis as an explanation of the repro- 

 ductive organs of Agalma while Allman excludes Agalma and brings forward the hypothe- 

 sis as an explanation of the nature of the reproductive organs of quite different forms, 

 is in itself enough to raise a suspicion that the whole conception is unscientific and 

 fanciful. 



As Bohm has shown in his valuable paper on the Leptomedusre of Helgoland (9) that 

 there is no such resemblance between the various stages in the development of a me- 

 dusa-bud and the stages in the development of the reproductive organs of a Leptomedusa 

 as Allman's hypothesis requires, it seems unnecessary to give any other reasons for 

 rejecting it. Although Allman has devoted a paper to the attempt to show that the 

 Geryonidae are blastochemes (6), the life-history of Liriope, as I have detailed it, is 

 absolutely irreconcilable with the belief that it is a cormus, and the hypothesis is com- 

 pletely overthrown by the recent discovery (76) that in many cases, the ova of the Lep- 

 tomedusa 1 arise in the proboscis and migrate along the radiating canals to the ovaries. 



One of the oldest opinions upon the relation between the hydra and the medusa is the 

 one which Huxley adopts (34), that the medusa is a free locomotor reproductive organ. 

 This is almost the opposite of Allman's view, that the reproductive organs of a medusa 

 are themselves persons, and that the medusa is in reality a community. Huxley says 

 (34, p. 149), "A medusoid, though it feeds and maintains itself, is in a morphological 

 sense simply the detached generative organ of the hydrosoma on which it is developed," 

 and on p. 31, "Morphologically the swarm of medusas thus set free from a hydrozoon 

 are as much organs of the latter as the multitudinous pinnules of a Comatula, with their 

 genital glands, are organs of the echinoderm." 



The authors who have accepted this view have appealed to the fact that we have a 

 complete series of species which present all the intermediate stages between the simple 

 reproductive prominences of Hydra and the live sexual medusa of Turritopsis orEutima. 

 In Hydra the reproductive organ is simply a protrusion from the surface of the body; 

 in Eudendrium it is more prominent and it contains a stomach-like outgrowth from the 



