43 GENERAL HISTORY OP 



Siebold remarks, that Ehrenberg insists much on the red colour as 

 a distinctive indication of a visual organ, but erroneously so, since 

 other colours prevail in the unquestionable eyes of Insects and 

 Crustacea, such as blue, and sometimes violet or green. 



Moreover, the admission that Infusoria possessing eye-specks have 

 a general sensation of Hght, does not prove the optical nature of 

 those specks, because forms, destitute of them, exhibit a like sensi- 

 bility of the presence of light, and fiu'ther, as Siebold observes, if 

 sight be limited to the simple discrimination of light from darkness, 

 this faculty might be secured, without any optical apparatus, by the 

 entii'e sensitive surface of the body. 



According to Morren, the red pigment spots of Lagenella, Crypto- 

 glena, and Trachehmonas, cannot be eyes, as in the last, the colouring 

 matter may be distributed over the whole body, when the animal, 

 on this supposition, would be changed, in toto, into an eye. 



The very recent and extended researches of M. Thuret (Sur les 

 Zoospores, in " Annales des Sciences jSTaturelles," vol. xiv. Z^^ series, 

 1850,) on the reprodxictive gems, or Zoospores of Algae, prove these 

 bodies to possess red eye-like specks, resembling to those seen in the 

 Polygastrica, but which disappear when the Zoospores attach them- 

 selves, and germination proceeds. These bodies, moreover, direct 

 themselves, in general, towards the light, and thus exhibit the same 

 fonn of sensation of its presence, as do the Polygastrica themselves. 



The general sense of contact possessed by the bodies of the 

 Polygastrica, would oftentimes seem to exist in a higher degree in 

 their cilia, proboscides, and other processes, just as in the tentacula 

 or feelers of insects ; and so far such processes are special organs of 

 sensation. But even the cilia, and the proboscides of the flagelliform 

 variety, are not peculiar to the animal Polygastrica, for they are also 

 found as processes of Zoospores in many Algae. 



Section- XVI. — Pcproduction of Polygastrica. — Monas vivipara is, 

 according to Ehrenberg, the only species of this class that is 

 viviparous, though some moAdng granules observed amongst the 

 Bacillaria, have been supposed by him to extend this condition. 

 "With this exception, they may be termed o^iparoixs, though besides 

 the formation of eggs, which is a very fertile mode of increase, they 

 also propogate, by means of a self-di^■ision of the body of the 



