of Insects and Crustaceans 4nimak< 155 



shaped extremities of the optic nerve. A similar structure 

 probably exists in all the Monoculi, and most of the inferior 

 Crustacea. In the Daphniae the crystalline bodies are pear- 

 shaped, short, and few in number; such also is the case in 

 Gammarus pulex. In all, the principal peculiarities, inde- 

 pendent of the absence of facets on the cornea, consist in the 

 anterior rounded extremities of the crystalline cones, and the 

 manner in which they project anteriorly beyond the stratum of 

 pigment in which their apices are immersed ; to which, how- 

 ever, there are some approximations in insects. Are these 

 peculiarities connected with the aquatic habits of these 

 animals, rendering necessary a greater refractive power? 



The pear-shaped masses in the Daphniae and Gammarus 

 pulex present an approach to the lenses of simple eyes, as 

 they occur (aggregated) in Oniscus, &c. The latter, however, 

 besides possessing a spherical lens, have a round vitreous 

 humour, and never the transparent conical masses. The 

 difference from these aggregates is still greater in Monoculus 

 apus, the cones being elongated, small, and numerous. Hence 

 it becomes necessary to discriminate the compound eyes with- 

 out facets, of the inferior Crustacea, as well from the compound 

 eyes with facets of insects and Crustacea, as from the aggregates 

 of simple eyes in Millipedes and Onisci. 



Ueber den Ban der Augen bei Murex tritonis, Linn., vom 

 Dr. J. Mtiller zu Bonn. (Meckel's Archiv, No. 3, 1829. 

 On the Structure of the Eyes in Murex tritonis.) 





fTVHE black points at the extremities of one of the pairs of 

 feelers in Helix pomatia, were long ago described by Swam- 

 merdam as eyes, in which he recognised an aqueous humour 

 and a crystalline lens. Subsequently, Stiebel ( ' Meckel's 

 Archiv,' b. 5) examined the same parts in Helix pomatia 

 and Cyclostoma viviparum, and found in them a choroid, an 

 iris, and a crystalline. As the true nature of these supposed 

 eyes of gasteropodous mollusca was, however, still by many 

 considered problematical, Dr. Mulier availed himself of an 

 opportunity of deciding the question by examining them in 

 Murex tritonis. 



They are here placed at the outer side of the feeler, on a 

 small eminence near its root, the axis of the organ being in the 

 same direction as that of the feeler itself. The surface of the 

 eye is convex, and surrounded by a prominent ridge formed 



