STUDIES ON SPATHIDIUM SPATHULA 193 



of the cell. Accordingly, since li\dng animals, studied under 

 the highest powers and manipulated with the Barber micro- 

 dissecting apparatus, stained total mounts, and serial sections 

 fail to reveal the presence of trichocysts, we are forced to con- 

 clude that they are not present.^ 



Although trichocysts were discovered b}^ Ellis^'' as long ago 

 as 1769, given their present name by Allman^^ in 1855, and sup- 

 posed to be 'poison organs' by Lachmann^- two years later, there 

 is to-day little conclusive data in regard to their function. Even 

 in forms like Paramecium and Frontonia with obviously highly 

 developed trichocyst apparatus, so far as we are aware, the func- 

 tion of the trichocysts is chiefly a matter of assumption. Mast 

 clearly showed that the trichocysts of neither of these organisms 

 have any paralyzing effect on Didinium, and attributed to them 

 merely a mechanical effect in that they form a viscid mass about 

 the organism which hampers its enemy. Indeed, Jennings stated : 

 "It is possible that the discharge (of trichocysts) is really an 

 expression of injury, — a purely secondary, even pathological 

 phenomenon, like the formation of vesicles on the surface of an 

 injured specimen. "^^ 



On the authority of Balbiani,^* trichocysts were stated to occur 

 in Didinium until Thon,^^ corroborated by Mast,^^ demonstrated 

 their absence. However, Thon believed that Didinium has a 

 paralyzing effect on a Paramecium which has been struck by the 



' L. L. Woodruff and Hope Spencer, The food reactions of the infusorian 

 Spathidium spathula. Proc. Soc. Exp. Biol, and Med., 1921, vol. 18, p. 183. 



1° J. Ellis, Philosophical Trans. Royal Society, 17fi9, vol. 59, p. 144. 



" G. J. Allman, On the occurrence among tiie Infusoria of peculiar organs 

 resembling thread-cells. Quart. Jour. Microscopical Science, 185.5, vol. 3, 

 p. 177. 



12 J. Lachmann, Annals and Magazine of Natural History, 1857, vol. 19, p. 126. 



'3 H. S. Jennings, Behavior of the lower organisms, 1906, p. 91. 



»^E. G. Balbiani, Observations sur le Didinium nasutum. Arch. d. Zool. 

 Exper. et Gen., 1873, T. 2, p. 363. 



1* K. Thon, Ueber den feineren Bau von Didiniiun nasutum. Archiv f. Pro- 

 tistenk., 1905, p.289. 



1*^ S. O. Mast, The reactions of Didinium nasutum (Stein) with special refer- 

 ence to the feeding habits and the function of trichocysts. Biol. Bull., 1909, 

 vol.16, p. 91. 



