Nervous System of the Infusoria. 6^ 



SchoefFer had previously observed the several parts of the 

 brain of the Daphnies, better even than J urine. But the for- 

 mer of these observers had given to the brain too many por- 

 tions, as the latter had described too few ; for Schoeffer errone- 

 ously regarded the feelers of the females, which are inclosed in 

 the lower and truncated part of the forehead, as a third part of 

 the brain, whilst Jurine had recognised the true nature of these 

 organs, but had not discovered the middle part of the brain 

 which supports the small eye, and no more had he seen this eye 

 itself Mr Strauss, moreover, had not perceived that portion of 

 the feelers which is hidden, he had only seen and delineated their 

 projecting extremities. In many species he mistakes the optic 

 nerve for the simple eye ; and he regarded that eye as a simple 

 point or black spot, although it presents the same organization 

 as the eye of the Cyclops, which he himself regards as the eye, 

 and though that organ possesses an optic nerve which is very 

 distinct. Mr Strauss has represented that eye as nearly of the 

 same form as in all the species of the Daphnies, while M. 

 Ehrenberg is satisfied that, according to the different species, 

 there is a great difference in this point ; and besides, the colour 

 of this simple eye is not black, but red, sometimes bright and 

 sometimes dark. 



Whoever will attentively examine the eyes of the Daphnia 

 and the Cyclops, which may very well be done with a magnifier 

 of 200 power, will find as much reason to conclude that these 

 organs have eyes in them, as he has for considering as such the 

 simple eyes of the Diptera. And after this he can entertain no 

 doubt concerning the function of the red points in the Rotatoria, 

 and other Infusores, even down to the Monades. Doubts on 

 the point are solely the consequences of an imperfect knowledge 

 of the connection and extent of the organs of the same name in 

 other animals. 



It is quite natural that the spot of coloured pigment should 

 have been observed previous to the optic nerves, which are co- 

 lourless and transparent ; but we are not authorized to admit 

 the real absence of these nerves, which are often invisible on ac- 

 count of their minuteness and their transparency, and also on 

 account of the opacity of the parts which surround them, in 

 the places where the coloured points exist. On the other hand, 



TOL. XX. NO. XXXIX. — JANUARY 1836. E 



