20 DISCOPHORiE. Part IH. 



say positively; but it seems quite probable that the former is the case. The degree 

 of contractility which the embryo possesses is shown by Fic/s. 8 and 8", which Avere 

 taken from the same individual. 



In an immediately subsequent phase a totally new form j^resents itself: by the 

 flattening of the scyphostoma it assumes a shape {Figs. 9 and Q'') which strongly 

 reminds one of the blood discs of birds and reptiles; and were it not that the 

 two sides of the oval planula are simply concave, the resemblance would be complete. 

 The anterior end {Fig. Q'' c) is a little thicker than the posterior (c^), and the middle 

 is the thinnest and occupied by a clear oval mass. The motions of the planula 

 are just as rapid and varied as in the last stage, but much more remarkal^le, on 

 account of the alternate presentation of its sides and edges to the eye in rapid 

 succession while it rotates ujion its longer axis. The anterior end of the body 

 soon becomes much thicker {Fig. 10" c), and, when seen edgeways, presents an 

 angular outline and flat area at the extreme end (c). At the posterior end (e^), 

 however, it does not change much in form. In an end view of the anterior end 

 {Fig. lO*"), the outline is oval ; the posterior end {Fig. 10") is also oval transversely 

 but not so thick proportionally. In the middle of the flat area {Fig. 10" c) there 

 is a cup-shaped depression {Figs. 10 c, 10*" c, and 10* c), which will at once be 

 recognized as the mouth in its inci^^ient state. Excepting the outer transparent 

 layer, the Avliole body is very opaque. In a quiescent state the stiffened, bristle-like 

 appearance of the cilia {Fig. 10'^) calls to mind a similar phenomenon observable 

 among infusorial fonns.^ At this stage the embrj'O terminates its free wandering 

 life, and it may be seen diligently seeking a place to lay its foundation; for such it 

 truly has, as we shall presently show. 



The Scyphostoma^ of Aurelia and Cyanea. We now proceed to describe the 

 development of the scyphostoma of Cyanea and that of Aiirelia together. The 

 wandering life of the planula form having come to an end, we may observe it set- 

 tling down upon its narrower end {Figs. 10 and 10* c^) : it wavers, and sways to 

 and fro as if it Avere trying to force its Avay doAvnward into the substance upon 

 which it has fastened itself, and then, as if dissatisfied Avith the promise of a good 

 basis for its foundation, it suddenly loosens its hold and SAvims aAvay to another 

 locality, there to repeat the same kind of examination, until finally, after perhaps half 

 a dozen attempts, as we have observed, it finds a suitable place to rest upon jierma- 

 nently. In the process of attaching itself, the posterior end {Fig. 11 c^) becomes 

 simply flattened, or moulded to the shape of the body to Avhich it adheres.^ The 



* Ehrenberg has actually mistaken the embryos - See Vol. III., page 80, for the meaning of the 



of Aurelia for parasitic Infusoria. Die Acalephen word Scyphostoma as used here, 

 edsot hern Meeres, Berlin, 1836, pp. 20 and 77. * Siebold loc. cit. page 28, states that this end 



