68 SUMMARY OF CUERENT RESEARCHES RELATING TO 



the thin margin of the disc there are eight marginal bodies ; the surface 

 of the disc has a network of rather deep grooves. The arm grooves unite 

 by pairs into four short perradial grooves which lead to the four-sided 

 mouth, which is 12 mm. broad. Thence a short oesophagus extends 

 through the arm disc, and divides into four branches which enter the 

 four divisions of the arm, where they are very small and oval in trans- 

 verse section. They open into a large central gastric cavity, which is 

 only from 3-5 mm. high. Sixteen vessels arise from the central stomach, 

 and all open into the circular canal which is distant 135 mm. from the 

 central point of the Medusa. From this canal blind canals pass towards 

 the centre. The zone outside the circular canal is occupied by a close 

 vascular plexus, which is traversed by continuations of the perradial and 

 interradial canals. 



The subumbrella is provided with circular folds which act as brood- 

 spaces and are generally filled with embryos. 



The mesogloea is colourless ; on the outer surface of the disc there 

 are numerous round papillae, separated from one another by deep grooves 

 which are invested by violet epithelium. These grooves form a network 

 which extends over the surface of the disc, and gives it its violet colour. 



The author is inclined to think that Haacke's Monorhiza is synony- 

 mous with his genus ; he forms for it the new family Chaunostomidae 

 which he places between the Cassiopeidse and the Cepheidse. 



A full account is given of Phyllorhiza punctata from Port Jackson ; 

 it appears to be most nearly allied to Toxoclytus and Lychnorliiza, but it 

 differs in the possession of a continuous subgenital space, a character to 

 which Dr. von Lendenfeld attaches less systematic importance then does 

 Haeckel. Some additions are made to our knowledge of Cramhessa mosaica, 

 corrections of several of Haeckel's characters being made. This species 

 is remarkable for having two varieties, one blue, one brown ; the former 

 is found in Port Phillip, and the latter in Port Jackson. Numerous as 

 individuals are in both these localities, the author never found a brown 

 example at Port Phillip, or a blue one in Port Jackson. 



In an account of the structure of the three just mentioned species, 

 and of the Rhizostomata in general, the disc and locomotor apparatus was 

 first considered. The disc differs in structure from that of other Medusae 

 only by always wanting tentacles, and generally having no mouth on the 

 under surface. All the species have large discs, and these are often 

 brightly coloured. In the epithelium of the exumbrella we find several 

 layers of high cells ; in the region of the marginal bodies, and especially 

 in the dorsal sensory pits, there is a specially differentiated sensory 

 epithelium. The epithelium consists of an outer layer, composed of 

 supporting cells, goblet, sensory, and stinging cells, and of a subepithe- 

 lium, which is best developed in the projecting parts, and consists of 

 young cnidoblasts, ganglion-cells, indifferent (?) cells, and, in Gassiopea 

 polypoides, of muscle-cells. These are all separately described ; the 

 sensory cells are delicate spindle-shaped elements from the upper free 

 end of which a rather long conical tactile seta projects ; at the base is a 

 multiramified stalk. Osmic acid gives rise to the appearance of granules 

 similar to those seen by Jickeli in the sensory cells of Hydroids. The 

 subepithelium of the exumbrella contains fibrils which have a tangential 

 course, and which may possibly be nerves. 



The mesogloea is solid, and consists of a structureless ground-mass in 

 which fibres and cells of various kinds are found. There can be no 



