28 THE PSYCHIC LIFE 



globule, acting as a crystalline humor, and surrounded 

 by a red pigment, acting the part of the choroid. 



Before M. Kiinstler, Claparede and Lachmann, 

 in their important work on Infusoria and Rhizopods, 

 had described a similar visual organ in the Freia ele- 

 gans, a ciliated infusory of the family of Stentorines. 

 " Immediately behind the point of truncation," say 

 they, " there is found a lunate spot of intense black, 

 evidently belonging to the category -of those phenom- 

 ena which M. Ehrenberg, in the Ophryoglenae, for ex- 

 ample, calls an eye or an ocular spot. The significance 

 of this spot has never been known. It was often very 

 much denser than that of the Ophryoglenae, and some- 

 times there was discovered behind it a very trans- 

 parent corpuscle, which involuntarily gave rise in the 

 mind to the idea of a crystalline humor. We cannot, 

 however, add much of importance to this idea, since 

 the functions of a refracting apparatus must neces- 

 sarily remain problematic, as long as we do not dis- 

 cover behind it a nervous apparatus fitted to perceive 

 the impressions received." 



This last conclusion seems to us excessively cau- 

 tious. The co-existence of a pigment and of a crys- 

 talline humor amply suffices to characterize a visual 

 organ. As to the nerve apparatus susceptible of per- 

 ceiving impressions, it is replaced by the protoplasm, 

 which, as is well known, is sensitive to light. 



Even before that, in 1856, Lieberkiihn had discov- 

 ered in a ciliated infusory, the Panophrys flavicans, 

 an ocular spot, composed of a convex crystalline 

 humor, having the form of a watch-crystal enveloped 

 by pigment and placed on the convex side of the oral 

 fosse. In another species, the Ophryoglena atra, he 

 found black pigment, but no crystalline humor. 



