﻿296 CONTRIBUTIONS TO THE NATURAL HISTORY 



their envelope is cast from the ovary, the yolk undergoing the whole process of division 

 before the eggs are laid, and the germ, when thus hatched, having a somewhat ovate 

 form, but still a very uniform homogeneous structure. Such germs, recently hatched from 

 e^s, I have seen move slowly, then attach themselves to the solid bodies in the jars in 

 which they were kept, and grow into a Campanularioid polypidom, the history of which I 

 shall give in another part of this paper. After the eggs have been laid, the ovaries are 

 considerably reduced in size, and presently dissolve, when the animal soon dies. When 

 forming, the eggs present all the characteristic structure of eggs in general, and hang 

 in bottle-shaped sacs from the lower surface and the sides of the chymiferous tubes. 

 I would only add, that I have repeatedly noticed a minute dot within the germinative 

 spot; but of all the changes which the eggs undergo, I shall speak more fully when 

 illustrating their metamorphoses. 



Notwithstanding the very flattened form of the disk when compared with that of 

 Sarsia, we may trace in these little spreading bells the same general arrangement of 

 muscles as in Sarsia and Hippocrene. But it requires greater care to trace it fully, 

 and it is more difficult to reproduce, in distinct appreciable drawings, the bundles which 

 have been traced in highly contracted and distorted dead specimens. However, it is 

 easy, in the first place, to see in living specimens, that the movements are entirely the 

 same, and that the differences arise chiefly from the energy with which they are per- 

 formed, in connection with the different permanent shape of the gelatinous disk. This 

 disk being flatter, its margins thinner, and the lower partition, which extends inwards 

 from the margin within the tentacles, narrower, the partition controls less powerfully the 

 general motions than is the case in either Sarsia or Hippocrene, in neither of which do we 

 ever see the lower partition unroll and turn inside out, as is so frequently noticed in 

 Tiaropsis. This arises from the circumstance, that the partition is not only more lax 

 and floating, but also narrower in comparison with the width of the gelatinous disk, and 

 its spreading form. The muscular fibres in this partition are, as in the other genera, 

 concentric and circular, combined with fewer radiating ones. The concentric fibres are 

 by far the most prominent ; their linear arrangement and cellular structure are easily 

 seen, perhaps with even more ease than in any of the other types (Plate VI. Fig. 18). 



The muscles of the disk are arranged precisely as in Sarsia or Hippocrene. There 

 is an external superficial system of bundles hanging over the gelatinous mass, and sim- 

 ply covered by an epithelial film, which forms the outer coating of the body. This sys- 

 tem is particularly loose and difficult to trace towards the periphery. This difficulty 

 arises from the unfolding of the disk near its margin, where it is thinned out and 

 readily bent outwards, and even upwards, as soon as the dying animal sinks and lies 



