176 RAMBLES OF A NATURALIST. 



Ehrenberg had regarded as organs of vision certain 

 coloured points which are met with in the margin of 

 the umbrella in the Medusae, at the extremities of 

 the rays in the Star-fishes, in the head among the 

 Annelids, Planarias, Rotifers, &c., and at one of 

 the extremities of the body in certain of the Infu- 

 soria. The accuracy of most of these statements was 

 denied in the most positive manner, although often 

 very unjustly. In proportion as these creatures have 

 been more profoundly studied, it has been found, in 

 the case of those animals whose size rendered them 

 accessible to our methods of examination, that the 

 greater number actually possessed true organs of 

 vision. The most abundant evidence on this point 

 has been contributed by naturalists of every Euro- 

 pean nation. 



The Annelids more especially furnished me with 

 a very striking example of this fact. One of the 

 species, which lives in the Sicilian seas, possesses 

 eyes which are almost as complete as those of a fish. 

 I have succeeded in enucleating the crystalline lens, 

 and in examining it separately ; and I found that 

 when it was placed upon a piece of thin glass which 

 received the parallel rays transmitted to it by a plane 

 mirror, it formed perfectly achromatic images. These 

 images repeated and magnified by the microscope 

 enabled me to distinguish with perfect clearness the 

 very smallest details of the neighbouring coast, and 

 by means of the crystalline lens of an Annelid my 

 microscope was thus converted into a telescope. 



The opposition which Ehrenberg met with was 

 even more strongly marked when he announced that 



