CNIDARIA 123 



to the power of sexual reproduction, that of non-sexual 

 repi-oductiou bj budding and division. In reproduction by 

 means of transverse division, the basal peduncular entl of 

 the divided polyp must have reproduced a new oral part, 

 whereas the detached oral portion had to move away from 

 the place of its origin and seek a new place of attachment. 

 Before it could attach itself, however, it must by growing 

 have reproduced the apical part of the goblet- shaped body 

 and the stalk, so that in this way there arose two individuals 

 of the same form as the parent. In this migration of one of 

 the offspring of the division was furnished the motive for 

 its metamorphosis in the direction of an increased power of 

 locomotion, whereby a difference between the form of the 

 attached polyp and that of the free-swimming medusa was 

 initiated. Prom what has been said it is not to be wondered 

 at, that the two forms are connected by gradual transitions ; 

 nevertheless we shall have to adhere theoretically to the 

 differences of these two morphological conditions. The 

 medusa is therefore a morphological phase of the Scypho- 

 zoa which has proceeded from the scyphopolyp; but, owing 

 to the assumption of free locomotion, it is more highly deve- 

 loped, the presence of sensory bodies and marginal lobes 

 and the more highly organized musculatui-e of the sub- 

 umbrella, with concomitant increase of the elastic mesogla-a 

 of the umbrella, being characteristic of it. 



In the Calycozoa the scyphopolyp reaches its highest 

 phase of development, whereas the Peromedusae are to be 

 looked upon as the most primitive medusa forms. The lat- 

 ter still reproduce the elongate bell-shaped form of tlie 

 umbrella, with its apical, stalk-like process, derived fr-omthe 

 attached polypoid ancestral forms, and in the possession of 

 large septal funnels resemble the scyphopolyps, whereas 

 the development of the margin of the umbrella marks them 

 as medusae. In contrast to them, the Ephyropsidge and the 

 corresponding larval Ephyra form appear as a further stage 

 in the developmental series, in which the apical, elongate 

 bell-shaped part of the umbrella and the peduncular rudi- 

 ment have been lost, and in which the septal funnels have 

 degenerated. We must explain the four interradial points 



