Microscopical Society of London. 811 



M. Livois. He then described the Echinococcus from his own ob- 

 servations, first premising that the walls of the hydatid cyst in which 

 the animalcules are contained, consist of a transparent colourless mat- 

 ter, deposited in very fine laminae, the innermost being more delicate 

 and more easily detached than the outer ones. Under a high power 

 these laminae are found to be composed of a finely granular material, 

 resembling coagulated albumen. Numerous small opaque masses are 

 seen disseminated irregularly in the walls of these cysts, and to the 

 inner surface are attached the Echinococci in small bundles or mass- 

 es, consisting of from five to twenty individuals, attached by short 

 pedicles to a common central mass, which again is prolonged into a 

 short common pedicle, by which the whole is attached to the interior 

 of the parent cyst; the innermost lamina, however, appears to be pro- 

 longed over the masses of Echinococci and their pedicles, thus af- 

 fording them a delicate envelope. These polypoid masses of Echi- 

 nococci are composed of numerous distinct individuals, which occur 

 in two forms ; namely, with the head (which is surrounded with a 

 circlet of spines) either protruded or retracted : the latter is the con- 

 dition usually observed, the other position appearing to be the effect 

 of a post mortem change. The Echinococcus with the head retracted 

 exhibits an ovoid form, flattened at the poles, and having a depres- 

 sion or notch more or less evident in each. The body consists of an 

 internal granular substance, apparently of different density in differ- 

 ent parts, and enclosed in a thick external tunic, the outer surface of 

 which presents no trace of cilia and is smooth ; the internal surface is 

 more irregular or rough, and between it and the internal granules are 

 situated certain transparent oviform bodies, whose office does not 

 appear. With regard to the mode of propagation or development of 

 these animals, the author stated that the opinion entertained was that 

 these aggregate masses were probably a stage in the development of 

 the animalcule, the earlier and later periods of which demanded fur- 

 ther observations ; and thus he was disposed to agree with Siebold in 

 his view of their proceeding from a sort of gemmation from the parent 

 cyst. The way in which these Entozoa become disseminated in the 

 animals they inhabit, he also stated to be a subject as yet involved in 

 obscurity, as well as many other points of their natural history. 



Dec. 11. — Professor Bell, President, in the chair. 



A paper by the Rev. J. B. Reade, " On Animals of the Chalk still 

 found in a recent state in the stomachs of Oysters," was read. 



After some introductory remarks, Mr. Reade stated that a conside- 

 ration of the well known ciliary currents in the fringe of the oyster, 



