162 Proceedings of the 



or sac from the canal of the body, formed of all the three elements. 

 This diverticulum was developed into a polype body, with mouth and 

 tentacles like those of the polype, from which it pullulated ; the two 

 bodies having the digestive canal and all the tissues continuous with each 

 other. In Hydra tuba, multiplication took place by stolons, which ex- 

 tended to some distance from the body before the new polype bodies 

 sprouted from them, but in that case also a prolongation of the intestinal 

 element passed through the stolon from the old into the new body. These 

 new polypes were not young ; their production was a simple increase of 

 the individual, becoming afterwards a multiplication, either by accident, 

 in some cases, or in others by a natural process of absorption. The 

 structure of the helianthoid zoophytes or Actinias was more complicated 

 in its development than that of the hydroid polypi, but it consists of the 

 same three elements. The dermal coat was succeeded by the muscular 

 element, which constituted the chief part of the external wall of the body 

 and tentacles, and then passed inward to the stomach, in the form of septa 

 or partitions, which suspended that viscus in the centre of the body, and 

 divided the intervening spaces into numerous chambers. The mucous or 

 intestinal element existed as a flattened sac or stomach, which appeared, 

 when viewed edgeways, as a mere line extending down about half the 

 centre of the body. The stomach communicated freely with the general 

 cavity of the body. This cavity, which corresponded to the water-vascular 

 system of the Acalephse, was single below, but as it passed upward it 

 formed a number of chambers divided from each other by the septa before 

 mentioned, and finally communicated with the tentacles, each chamber 

 terminating in the cavity of a single tentacle. 



The whole of the general cavity and its chambers was lined with cilia,, 

 by which a constant circulation of the fluid was sustained, and the func- 

 tions of nutrition, respiration, and excretion were all carried on simulta- 

 neously. From the lining membrane of the general cavity, the male and 

 female reproductive organs were also developed, and there, in some spe- 

 cies, the ova were hatched, and the young (at first mere shapeless, ciliated 

 germs, swimming rapidly in the fluids of the cavity, chambers, and ten- 

 tacles) became fully formed, passed into the stomach of the parent, and 

 were ejected from the mouth as perfect Actinias, with mouth, tentacles, 

 and suctorial foot. The author had thought it possible that the prolon- 

 gations from the foot of Actinia lacerata might contain one of these 

 hatched germs in its imperfect state, and that it might be thus deposited 

 on the surface occupied by the parent, and its safety insured. Having 

 some specimens of dianthus in his possession, he had waited for some time 

 in vain for their multiplication by fissure ; he therefore determined to 

 try an eccperimentum cruris, and for that purpose having placed the spe- 

 cimen in a jar of sea- water, and fed it until it had become fully distended, 

 he examined the edge of the foot, which was perfectly transparent, with 

 a powerful lens, and convinced himself that no ovum or germ existed in 

 that situation. He then separated a piece about a line in length, by half 



