INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 455 



a lip-liko fold, and to the oesophageal grooves which pass downwards 

 from the two angles of the mouth ; these are richly ciliated, and as 

 they remain open when the mouth is closed, it would seem that they 

 are the means of conveying a constant current of water into the 

 interior of the body. 



In structure the cesophagus agrees very largely with the oral disk, 

 but as the musculature disappears only two ectodermal layers are 

 present in its walls; the epithelium, though thick, is in a single 

 layer ; the glandular cells are either coarsely granulated, or form 

 clear spaces club-like in appearance, provided with a delicate 

 membrane, and containing an open protoplasmic meshwork. Further 

 investigations are required to demonstrate the extent of the con- 

 nection between these two sets of cells. From the nervous layer 

 ganglion colls are almost completely absent. The mesoderm is 

 developed at points into longitudinal ridges, and the endoderm is 

 provided with a circular layer of muscles, but there is not at the 

 lower, any more than at the upper, end of the digestive tube any 

 special sphincter muscle. 



The Septa and the parts appended are the most complicated 

 parts of the organization of the Actinife ; they are provided with a 

 supporting tissue of fibrous connective substance, which is invested 

 on either side by a layer of muscular fibres and of epithelium, 

 closely connected with one another ; at their free edge they are 

 continued into the mesenterial filaments with their acontia ; and, 

 finally, in their interior there are developed the generative organs. 



The^^roMs connective substance is derived from the adjoining regions 

 of the body, strong fibrous bands breaking their way through the endo- 

 dermal musculature and running along transverse planes which are 

 separated from one another by feebly developed longitudinal fibres. 



The epithelio-musctdar layers present us with two systems of 

 muscles which are separated from one another by the suppoi-ting 

 lamella, and are distinguished by taking resj^ectively a transverse 

 and a longitudinal direction ; the latter are by far the stronger, 

 and the former arc oftentimes so feebly developed as to escape the 

 observation of investigators ; in a number of Actinia) the transverse 

 fibres often form a special parieto-basilar muscle, the presence of 

 which seems to be the cause of the sucker-shape of the foot-disk. 

 In the examination of the elements of the epithelio-muscular layer 

 Sagartia parasitica is the form in which it is most easy to make 

 out the characters of the muscular fibres and of the cpitli'elial cells ; 

 these two sets of elements combine to form the neuro-muscular, or 

 epithelio-muscular cell, as the authors prefer to call it ; each of 

 these cells boars a single flagcllimi of sonic size ; the cell itself may 

 form a short cylinder, or may be extraordinarily long, and between 

 these two extremes there are all kinds of intermediate conditions. 

 In addition to these there are three other sets of elements in the 

 tissues now under consideration ; those are the nettle cells, the gland 

 cells, and the neuro-cpitlielial cells. The last are those elements 

 which in their external cliaracters completely resemble the sensory 

 cells of the ectoderm ; but there still remain nervo-fibrcB and ganglion 



