100 CLASS III. 
observer, Dr F. Wii, found these threads im Hucharis (amongst 
the Beroécea) without perceiving any irritation on touching it. 
In many there is only a single oral aperture, placed in the center 
on the inferior surface of the body. In others many suctorial tentacles 
are seen, or the arms have apertures conducting to tubes, which, 
like vessels, fall into larger stems and finally open into a common 
cavity, the stomach (Rhizostoma Cuy.). From the stomach arise 
water-canals, which are provided internally with cilia. By some 
writers these have been regarded as blood-vessels: but far rather 
ought they to be considered as respiratory organs, since in part they 
open freely on the surface of the body. But, in addition, blood- 
vessels have been found, which, at least in Beroé!, lie round about 
the water-canals, surrounding them like a sheath. Here nucleated 
corpuscles have been observed (blood-corpuscles?) which however 
move only very slowly and irregularly. 
The sexual organs are distinct in the disciform Acalephes, but 
have in both sexes the same form. In quorea they lie in form of 
folded plates on each side of the water-canals which spring from the 
stomach, towards the inferior surface of the disc. In the eared 
Medusa (Aurelia or Medusa aurita) there are four cavities, opening 
below at the disc and which have been taken for respiratory cavi- 
ties, in which les a folded organ, that is, an ovary or a testis, 
according as it contains ova or spermatozoa; in most Acalephes the 
spermatozoa have the ordinary cercarial form. In other Acalephes, 
as Beroé, ovaries and testes are united in the same individual: 
here they lie along what are called the ribs, beneath the skin. 
The metamorphoses, of which we have already spoken above, 
are remarkable in young Medusw. The eggs, that pass from the 
ovaries along the canal of the arms to their folds, are collected here 
and carried about, for a time, by the mother in saccules which 
afterwards disappear®. The young animals quit these receptacles 
in the form of ciliated Infusories resembling Leucophrys or Bursaria. 
These swim freely about, but after a short time (two or three days 
according to SrEBOLD) become fixed by their thicker anterior ex- 
tremity which has a sucker. Next, the body becomes. cylindrical, 
transparent, and at the free end, which thickens, an oral aperture is 
1 [The blood-vessels described by Witt could not be seen by Forsrs, Huxuzy, 
Luvuckart, &c.] 
2 See the figures of EHRENBERG Die Akalephen &c. Tab. ut. fig.1. 2. Tab. viii. fig. 1. 
