64 M. Elirenberg's Researches on the Infusoria. 



tuation, appeared to him especially to settle the point, and to 

 prove the nervous nature of these organs. As early as 1831, 

 in his second dissertation, he had demonstrated that these red 

 points are the eyes, and he now supports this opinion by many 

 new proofs. In his former dissertation, he remarked that these 

 points always maintained the same situation, and that their form, 

 their colour, and their position, exhibited the strongest analogy 

 with the eyes of the young Entomostracea, of the genus Cyclops, 

 animals which had always been regarded as provided with eyes. 

 Though directed by this analogy, he, moreover, supported his 

 views by the granular structure of the substance of the pigment, 

 and by the size of the nervous knot upon which the double eye 

 of the Cyclops is placed, an organ of which no notice had pre- 

 viously been taken. But it will be still easier to perceive this 

 approximation by comparing these parts with the more delicate 

 eyes of the Daphnias. All the known species of Daphnias have 

 two kinds of eyes, as flies have. The large compound eyes, of 

 a black colour, are moved by four muscles, according to M. 

 Strauss, and by eight according to our author. 



Near these eyes a cylindrical prolongation, round before, may 

 be very distinctly perceived, which arises from the brain, and 

 which is to be considered as the optic nerve ; it is continued for- 

 wards by two fine threads, which enter directly into the middle 

 part of the eye ; the optic nerve reposes upon a large knot of 

 medullary matter ; from this a second and thick elongation 

 arises, which becomes thinner in its progress towards the middle 

 of the forehead. Immediately behind the termination of this 

 prolongation, a reddish or blackish spot is seen, of a round or 

 elongated form, which in its colour and substance resembles the 

 eyes of the Rotatoria. This spot has not been observed by 

 Jurine ; M. Strauss has exhibited it in an imperfect manner in 

 the Daphnia pulex^ and it has been more accurately observed by 

 Messrs Schceffer and Gruithuisen. The eyes of the Cyclops 

 have no resemblance to the composite eyes of the Daphnias, 

 whilst in a striking way they resemble the small points or eyes 

 of these same Daphnias, which may be called simple eyes in com- 

 parison of the others, which are larger, and provided with a 

 great number of facets. 



