466 



Balbiani on the Reproduction of Infusoria. 



in detail the phenomena of infusorial reproduction. To restore 

 to them their true significance it is enough that I should show, 

 by reference to pure and simple facts, that the infusoria couple 

 for the purposes of fecundation like most other animals. 

 .... We have seen that hermaphrodism is the rule among 

 Infusoria .... and in mode of fecundation they approach 

 certain gasteropods and worms, which, having both sexes united 

 in a single animal, nevertheless require the co-operation of a 

 second individual to produce fertile germs ; " but while these 

 latter are usually provided with well-developed organs for the 

 intromission of the prolific fluid, " the infusoria are totally 

 destitute of them,'" and to supply their absence, nature has 

 recourse to other means. Describing these, M. Balbiani divides 

 Infusoria into two classes — one having the mouth situated at 

 one anterior extremity of the body, and in the direction of its 

 longitudinal axis, and in others, which form the great majority, 

 this orifice is placed beyond the axis, on one side of the body, 

 and usually in its anterior half; and he speaks of the animals 

 coupling by bringing together the " depressed region placed 

 in front of the mouth ; or where it only exists in the form of a 

 minute and simple depression, or narrow groove, by the contact 

 of this part only, the remainder of the body being free. " The 

 exudation of a glutinous substance at the point of contact serves 

 to consolidate their adhesion, by soldering them intimately 

 together ; so that their premature separation becomes impos- 

 sible, notwithstanding the energe- 

 tic strains to which they expose 

 each other." At first he considered 

 the mouth was the organ for the 

 transmission of the fertilizing fluid, 

 and this opinion was strengthened 

 by noticing its position during the 

 process, but by examining the Pa- 

 ramecium aurelia with a good illu- 

 mination, and powers of 700 or 800 

 diameters, and treating the objects 

 with very dilute acetic acid, or aque- 

 ous solution of iodine, he states he 

 was " able to demonstrate that not 

 jr IC , i only the ovary, but also the testi- 



cle, was provided with an exccre- 

 tory duct, whose course he could follow, from its origin in 

 the glands to a point situated below the mouth, towards the 

 posterior extremity of the buccal furrow." The annexed sketch 

 (fig. 1) from M. Balbiani represents the appearance of two 

 Parauiecia aurelia slightly compressed, and acted upon by 

 dilute acetic acid : a is the ovary ; c its execretory duct ; b the 



