56 SUMMARY OF CURRENT RESEARCHES RELATING TO 



occupying tlie cell, and then consists of a basally barbed thread 

 and an apparently chitinons capsule with no protoplasmic con- 

 tents. Glandular cells also occur in the ectoderm here, as fusiform 

 or cylindrical bodies, sometimes bilobate, extending from the 

 surface of the ectoderm, — where they open, — to the mesoderm, 

 with which they have contact by a basilar process, usually swollen 

 at one point ; they vary considerably in appearance, being some- 

 times empty and hyaline, but generally more or less granular ; 

 they were found more abundantly in this species than in any other. 

 Peculiar to this species, were found some very delicate fusiform 

 cells, terminating in some cases in a fine cone ; they are compared with 

 the cells described as sensitive by Korotneflf from the chromatophores 

 of Actinia mesembryanthemum. Internally, the ectoderm is lined by a 

 mesodermic membrane which apjDears structureless in osmic acid 

 preparations ; in transverse sections it exhibits processes which pene- 

 trate the ectoderm at intervals ; in longitudinal section its outer border 

 is unbroken ; after treatment with alcohol it may be dissociated into 

 fine connective tissue fibrils ; it is probably an elastic membrane. 

 The mesodermic muscles consist of an external longitudinal, and an 

 internal circular set ; their fibres are indistinguishable from those of 

 the fibrous tissue. The endoderm, which is as thick in this species as 

 the ectoderm, is formed apparently of two layers, that of the ciliated 

 cells and a pigmented layer, but they are not really distinct ; for the 

 large and remarkably abundant pigment-corpuscles are arranged in 

 single series in long tubular cells, extending from the free surface, 

 where they terminate in cilia, to near the mesoderm ; here, however, the 

 pigment-globulss of the cell, which are orange-coloured, well defined, 

 and stain black with osmic acid, are replaced by a finely granular 

 protoplasm with a nucleus. The contraction of one tentacle when 

 pinched, without any participation in the movement on the part of the 

 rest, seems to the author to show the absence of a central nervous 

 system. 



Buccal Dish and (Esopliageal Tube. — Of the three layers which are 

 present here also, the ectoderm of the disk agrees essentially with that 

 of the tentacles ; but as it approaches the lip the thread-cells diminish 

 in number, and a form of gland-cell appears, which is only found else- 

 where in the oesophagus. The passage to the ectoderm of the oesophagus 

 presents no sharp line of transition in characters. The mesoderm is 

 more distinctly fibrous, and its nuclei more evident in the disk than 

 in the tentacles ; it has a festooned inner border, the result of circular 

 folds in it, which are lined by a layer of fine muscular fibres. The 

 endoderm agrees with that of the tentacles. The oesophageal tube is 

 thrown into regular longitudinal folds, of which each consists exter- 

 nally of ectoderm, and internally of a fibrous mesodermic process, 

 which is continuous with a septum on its internal aspect, and ends 

 freely in a mesenteric filament below ; in its ectoderm are found 

 sensitive cells, but almost no thread-cells or glands, the latter of which 

 are here replaced by cells containing protoplasm which stains deeply 

 with osmic acid. The mesoderm agrees with that of the disk, but is 

 looser in the folds above mentioned, and becomes very thin in the 



