82 ORGANIZATION OF THE INFUSORIA. 



From the foregoing account, as it appears in the ' Philosophical Transac- 

 tions,' vol. lix., for the year 1769, there cannot be the slightest doubt that the 

 bristle-like " fins," made suddenly to appear by the application of the acrid 

 geranium juice, are identical with the fine setaceous trichocysts characteristic 

 of the species described on a preceding page, any doubts that might exist 

 upon this subject being at once dissipated on reference to the characteristic 

 illustrations of the animalcule accompanying Ellis's description, and em- 

 bodied in Table VI., Fig. 5, a, b, c, and d of the volume quoted. In the 

 above connection John Ellis-has, however, not only to be accredited with the 

 first discovery of these supplementary structures, but, through the applica- 

 tion of the special means by which he efi*ected such discovery, he takes 

 rank as one of the first to make successful use of reagents, now so widely 

 employed in the elucidation of the more minute histology of the Infusoria. 

 In this direction, nevertheless, and as recorded at page 1 14, Ellis was to 

 some extent anticipated by another Englishman, Sir Edmund King, at so 

 early a date as the year 1693. 



The demonstration of the precise nature of trichocysts, and the con- 

 nection with them of their now generally recognized and characteristic title, 

 belongs to a comparatively recent epoch. In this instance also, however, an 

 Englishman is to the fore, such demonstration and titular denomination 

 having been accomplished at the hands of the present distinguished 

 President of the Linnean Society, Professor G. J. Allman, who, in the 

 'Journal of Microscopical Science' for the year 1855, described at consider- 

 able length the more minute characters and phenomena presented by these 

 bodies as met with in Bursaria {Panophrys) leucas. Here, as recorded by 

 him in the publication quoted, the trichocysts, now so-called for the first 

 time, were found to exhibit the aspect of minute fusiform bodies embedded 

 thickly and on a perpendicular plan of arrangement, as in the manner already 

 described of Paranieciiun. Under external irritation, such as the drying 

 away of the surrounding water, the application of acetic acid, or forcible 

 compression, they became similarly and suddenly transformed into long, 

 fine, hair-like filaments or setae, which projected from the whole periphery. 

 The rapidity with which the transformation from the fusiform to the 

 filamentous condition was effected, combined with the greater minuteness 

 and transparency of the objects examined, hindered for a considerable 

 while the recognition of the exact manner in which the process was 

 accomplished. At length, by carefully crushing examples and isolating the 

 trichocysts in their normal and fusiform condition, it was found that these 

 latter, after the lapse of a few seconds, became all at once changed with 

 a peculiar jerk, as if by the sudden release of some previous state of 

 tension, and assumed through this change a minute spheroidal shape. 

 After remaining in this condition for two or three seconds longer, a spiral 

 filament was next observed to become rapidly evolved from the sphere, 

 apparently through the rupture of a previously confining membrane, the 

 filament winding itself with such rapidity that the eye could scarcely 



