232 



the so-called Xanthidia found in sections of flint, and analogous to 

 the stellate sporangia of the allied family of the Desmidieae ; that con- 

 sequently the figures of the sporangia of the above-named species, as 

 given in Hassall's 'British Fresh- water Algae,' though perfectly correct 

 as far as they go, are only figures of the fruit in a transition state. 

 He suggested that as Zygnema quadratum is a species in which con- 

 jugation occurs between contiguous cells of the same frond, while, on 

 the contrary, in Z. varians it takes place between those of different 

 filaments, in all probability a similar change to that described ensues 

 with regard to the sporangia of all the species in both the sub-divisions 

 of the genus, and possibly in most, if not in all, of the family. 



Jmie 18, 1851. Dr. Arthur Farre, President, in the chair. 



A paper by P. H. Gosse, Esq., ' On the large Actinophrys of Eich- 

 horn, and on the Structure of the Flesh in the Polygastrica,' was read. 



After citing the observations of Eichhorn, to the effect that he wit- 

 nessed the capture of small Crustacea by the tentacles of this animal, 

 and the digestion of them within its body, which have been doubted 

 by later naturalists, the author mentioned that he had himself met 

 with the animal on two occasions, though it appears to have been un- 

 seen since the days of its first describer. Mr. Gosse then charac- 

 terized the species, to which he assigned the name of Actinophrys 

 Eichhornii. It is a whitish globe, distinctly visible to the naked eye, 

 and seen, under the microscope, to be studded all over its surface 

 with long, delicate, pointed, divergent rays. These organs have the 

 power of arresting, by mere contact, animals of much higher organi- 

 zation, which the author witnessed, and thus confirmed the testimony 

 of its discoverer. The paper went on to describe the rays as wholly 

 retractile within the body ; and other organs, in the form of clear oval 

 bladders, also capable of being protruded and retracted at various 

 parts of the surface; as well as vesicles contained within the substance, 

 and which, frequently inclosing food, evident!}' perform the part (the 

 author thinks only teinporarily) of stomachs. 



Mr. Gosse described the body of this animalcule as made up of an 

 aggregation of large, distinct, perfectly transparent, unnucleated cells, 

 pressing over and against each other, and thus rendered polygonal. 

 Their walls are not membranous, but composed of a semifluid viscous 

 mucus, resembling the bubbles on the surface of soapy water. This 

 substance is endowed with contractility, which the author proved 

 from several circumstances ; and he considered that the protrusile 

 bladders and the stomach-cells are only modifications of the common 



