some Fresliioater Ampliipods. 2;]3 



apparatus. Unfortunately the preservation in formalin had 

 so much damaged the internal nervous structure and the 

 brain that nothing definite can be said in this connection. It 

 is only possible to refer to the superficial appearance of the 

 eye, and in addition at most to the position of the dioptric 

 elements under the hypodermis as observed in preparations of 

 the entire animals under moderate and high-power magni- 

 fication. But even in this way interesting results are 

 obtained. 



In general the eye of Bathyonyx is not a compact organ, 

 such as we are accustomed to picture the compound eye of 

 Arthropods, but forms a large irregularly defined fleck of 

 unequal size with a variable number of crystalline cones in 

 each of the available specimens. I figure such eyes in 

 figs. 16-18. 



In fig. 16, which is drawn under a low magnification, 

 there are tAventy-four cones. Tiiey occur in a dark (brown 

 to brownish black) fine-grained pigment which appears to be 

 most thickly developed in the centre of the eye. 



Here was evidently situated the original eye, as, for example, 

 in (lammarus. In this central pigment most of the crystal- 

 line cones are collected, without, however, forming a compact 

 organ. 



They are as irregularly distributed in the pigment, without 

 any definite position, as the peripheral crystalline cones, 

 which mostly lie under the ordinary hypodermis without any 

 pigment. All the crystalline cones are commonly composed 

 of two segments or simply constricted, the hemispheres being 

 sometimes equal and sometimes unequal in size. Now and 

 again at the periphery small wholly isolated cones are also 

 found. The crystalline cones consist of a strongly refractive 

 homogeneous brownish substance, and therefore stand out 

 clearly in the preparations. 



In this condition the individual cones appeared in all four 

 specimens. Another eye, as seen under strong magnification 

 (as with Hom. Imm. Apochr. 01 j. 2 mm., Oc. 4) and showing 

 interesting details in the structure uf the cones, is reproduced 

 in fig. 17. 



Here the scattered components of the eye are still more 

 striking ; in the centre of the eye-fleck one finds large, simple, 

 rarely double, hexagonal or irregularly branched pigment- 

 cells in the midst of whose granular substance a small rounded 

 nucleus can be detected {p). The whole system formed 

 by the cones and the central pigment-cells retains in the 

 main a reniform shape, as is also typical of tiie compound 

 eyes of Gammarus. In Bathyonyx, however, there exists no 



Ann. (£• Mag. N. Hist. Ser. 7. Vol xx. IG 



