416 Microscopical Society. 



it as consisting of a green gelatinous and granular body, invested 

 by a highly elastic and contractile membrane, which is attached 

 by variable points to a hard siliceous shell, which was afterwards 

 stated by Mr. C. Varley to resist even the action of boiling nitric 

 acid. The form of Closterium is spindle-shaped, or crescentic — 

 the shell consisting of two horns, tapering off more or less to the 

 extremities, and united at the central transverse line — constituting 

 a perfectly symmetrical exterior. At the extremity of each horn is 

 an opening in the shell, which, however, is closed within by the mem- 

 branous envelope, wanting, however, in some specimens. "Within 

 the shell, and at the extremity of the green body, is a transpa- 

 rent chamber, containing a variable number of active molecules, 

 measuring from the 20,000th to the 40,000th of an inch ; these 

 molecules, or transparent spheroids, occasionally escape from this 

 chamber, and circulate vaguely and irregularly between the peri- 

 phery of the gelatinous body and the shell ; further, the parietes 

 of this chamber have a contractile power. The author denied the 

 existence of any papillae or proboscides at this part, as well as the 

 supposition of Ehrenberg that these moving molecules constitute 

 the basis of such papillae. He also denie^ the statement of the 

 same distinguished observer, that if colouring matter was mixed 

 with the water in which the Closterium resides, any motion was 

 communicated to the particles of such colouring matter by the sup- 

 posed papillae, or by the active molecules within the terminal cells. 

 A circulation of the fluids within the shell was observed, independent 

 of the vague movements of the active molecules ; this was regu- 

 lar, passing in two opposite currents, one along the side of the 

 shell, and the other along the periphery of the gelatinous body. 

 "When the shell and body of the Closterium was broken by pressure, 

 the green gelatinous matter was forcibly ejected by the contraction 

 of the membranous envelope. 



The action of iodine upon the specimens was very remarkable ; 

 1st, it did not, as reported by Meyen, stain the green body violet 

 or purple, but orange-brown ; 2nd, it produced violent contraction 

 of the investing membrane of the body, whereby the green matter 

 was often forcibly expelled from the shell at the transverse division ; 

 it instantly annihilated the motion of the molecules in the terminal 

 sacs, and the sacs themselves became so distended with fluid as to 

 burst, and allow the molecules to escape. 



The mode of reproduction was stated to take place, 1st, by spon- 

 taneous transverse division ; 2nd, by ova ; 3rd, by interbudding, or 

 the conjugation of two Closteria. 



