Royal Physical Society. 235 



ratus for the exercise of the faculties of motion, sight, hearing, 

 prehension, digestion, and reproduction. It will further have 

 the power of propagating animals similar to itself by gemma- 

 tion, from its alimentary polyps, as in Lizzia (fig. 13) ; from 

 its reproductive polyp, as in Thaumantias (fig. 14) ; and from 

 its tentacular polyps, as in Sarsia (fig. 15) ; and, lastly, in 

 these budding Acalephs, even while still attached, preparation 

 will have commenced for a still further exercise of the propa- 

 gative function. 



The ovaries or spermaries of Cordylophora and Clava are 

 the germens or anthers of the animal plant, while these Aca- 

 lephs must be considered as the fruit-bearing branches, lead- 

 ing an independent life. They are the divided parts, para- 

 doxically speaking, of an individual existence. 



15. Tlie umbrella (of the Acaleph of Eudendrium pusilla) is 

 homologous with, and developed from, the ectoderm of the 

 polypary. It is a clear, structureless tissue, containing, on 

 its external surface, numerous large thread-cells, each occu- 

 pying its own sac. It is continuous with the ectodermic layer 

 of the tentacular polyps, and exists as a delicate membrane 

 passing within the bell and partly forming the sub-umbrella, 

 and covering the alimentary polyp. 



16. The lateral canals (homologous with tubes of the endo- 

 derm in the fixed polypary) are situated immediately beneath, 

 and are adherent to, the umbrella. At the summit of the bell 

 they join together to form a quadrangular cavity, and they com- 

 municate below with a circular canal, which passes within and 

 around the mouth of the bell. This system of canals is at first 

 lined with red granular matter, which is afterwards absorbed, 

 and it is constantly traversed by streams of nutritive fluid, 

 impelled by ciliary action, and changing the direction of their 

 course at short intervals of time. 



^4 17. The sub-umbrella is a thin muscular membrane attached 

 to the exterior of the lateral canals on their inner aspect, and 

 along their whole length, and also to the umbrella along four 

 lines running mid-way between the canals. Its function is that 

 of motion ; it also acts as an organ of circulation and respira- 

 tion by enlarging the calibre of the lateral tubes at each of its 

 systolic contractions, and constantly refilling the bell with 

 vol. i. u 



