202 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Microscope it was seen to be a rhizopod-like organism with a rounded 

 cap ; that is to say, the larva proi:)er contained a colossal amoeboid cell 

 and a bell-shaped covering of flagellated epitlielium. The lar,[:je cell 

 gave ofl:* a number of homogeneous processes, many of which branched 

 or were flattened out at their free ends. Within there was a large 

 nucleus, closely resembling the central capsule of many Eadiolaria, 

 and this was invested in an elastic membrane, and had finely granular 

 contents. This large cell is the body which was spoken of by 

 Uljanin as the finely granular mass within the gastric cavity. The 

 further stages of development are characterized by the overgrowth of 

 the colossal amoeboid cells by the flagellated cells, and the con- 

 sequent formation of the oviform larva, which Uljanin regards as 

 the starting-point of his invaginate archigastrula ; but the author 

 points out that there is in it no round blastopore, but only a fine 

 slit ; this does not serve for the ingestion of nutriment but only 

 as a means of passage for the pseudopodia of the enclosed colossal 

 cell. The larvae, increasing in size, become elongated, and often 

 triangular in form ; the ectoderm is sharply separated from the 

 endoderm, and consists of a single layer of delicate flagellated cells ; 

 while the endoderm forms a single layer of cylindrical-flattened 

 cells. 



Gemmation commences even at this stage, a longitudinal section 

 revealing a diminution of the two germinal layers at the point where 

 the mouth of the first Medusa appears later on ; a well-marked pro- 

 jection at the oral pole forms the proboscis of the first Medusa-bud. 

 In later stages we find that the colossal cell is long persistent ; the 

 first sign of degeneration would apjiear to be the appearance of 

 several — perhaps renal — concretions; later on this degeneration 

 becomes gradually complete. 



The author is of opinion that the whole life-history of this 

 parasitic Medusa presents a series of secondary adaptations, which 

 are in causal connection with the parasitic habit ; the alternation of 

 generations is of a secondary nature, and the asexual generation is 

 characterized by the loss of the genital organs and of a number of 

 the other organs of a Medusa. 



Nervous System of Hydroid Polyps.* — C. F. Jickeli states that 

 he has discovered nervous elements in these, the only Coelenterata in 

 which they have not yet been observed. In the arms of the hydranths 

 of Eudendrium, he found between the flat ectodermal cells and the 

 longitudinal muscular fibres, branched cells, whence processes pass off 

 to a number of urticating cells, or become lost between the muscular 

 fibres; there is also a direct connection between the ganglionic cells. 

 He asserts the existence of a nervous plexus which is continued 

 forwards to the hypostome, and which extends also into the hydro- 

 phyton. Near the circlet of glandular cells at the base of the 

 hydranths there is a larger collection of ganglia ; but the connection 

 by nerve-fibres between the two w'as not made out. The nervous 

 system would appear to be confined to the ectoderm. 



* Zool. Anzeig., v. (1881) pp. 43-4. 



