32 Dr. Reid on the Development of the Medusse. 



of the body, is so thin that at first sight these processes appear 

 to be attached to the external surface. Fig. 16 is a greatly en- 

 larged view of one of these bifid processes. Each of these pro- 

 cesses forms two hollow floating tubes, communicating with the 

 stomach or internal cavity by a common orifice (fig. 16 a), and 

 having the edges of their external surfaces covered with nume- 

 rous filiferous capsules (fig. 16 Z>). The stomach is large and 

 extends nearly to the margin of the body or disc. Outside the 

 position of the four bifid processes, and on the lower surface of 

 the inferior wall of the body, there is a circular band, slightly 

 elevated, more granular and opake than the portion of the body 

 placed within it, having prolongations passing off from its outer 

 edge to the intervals between the eight bifid lobes or rays that 

 spring from the margin of the body, and others along the centre 

 of the lower surface of these bifid lobes, as far as the ocellus 

 placed at the point of bifurcation of each lobe (fig. 15). When 

 the animal contracts the marginal lobes in swimming, this circle 

 becomes narrower, more distinctly defined, and approaches nearer 

 to the mouth. In certain states of the animal the prolongations 

 from the outer edge of this circle to the intervals between the 

 eight bifid rays are longer than represented in fig. 15. When 

 the animal is examined in certain positions and with glasses of 

 weak power, this circle, and the sixteen prolongations extending 

 outwards from it to the intervals between the rays, and along 

 the lower surface of the rays themselves, assume pretty nearly 

 the appearances represented by Steenstrup as vessels ; and as I 

 have been unable to satisfy myself of the presence of any vessels 

 there, I am inclined to believe that he has been misled in this way. 

 I have occasionally observed the appearance of a thread-like 

 nervous circle around the mouth, sending a filament along each 

 of the rays towards the ocelli, on approaching which it bifurcated ; 

 but not having been able to make these out at other times, 

 under circumstances that appeared favourable for their detection, 

 I am not prepared to affirm that a nervous system is present. 



At the point of bifurcation of each of the marginal lobes or 

 rays there is placed, as Sars has described, a little eminence, hy- 

 pothetically designated by Steenstrup an ocellus (figs.l5c &17«). 

 This ocellus forms a mammillary process, consisting of three 

 distinct structures (fig. \7 a). The apex is chiefly formed of a 

 considerable number of very minute crystals, and a small part of 

 its base is more opake and more granular than its larger middle 

 portion. From a greatly enlarged view of the crystals occupying 

 the apex of the ocellus, given in fig. 18, it will be observed that 

 the upper are shorter and thicker than the lower ; in fact, while 

 a few of the former are almost as thick as they are long, some of 

 the latter are almost needle-shaped. On fixing the polarizing 



