644 William Patten 



to the calyx, wliere the former became coutinued ìnto the centre of the 

 crystalliue cone , while the latter , spreading- ont over the wall of the 

 calyx, form a complete network of nerve fibrillae ; the latter braneh, in 

 pretty regulär order, at rig-ht angles from the larger longitudinal ones, 

 and then unite to form a continuous network of superficial fibres (figs. 129 

 and 130). 



One finds in Galathea the same abaxial thickenings, (four),of the 

 calycal wall, as in Penaeus. and can readily distinguish in them the cross 

 fibrillae, which bave exactly the same appearance as those in the rods of 

 Pecten. In cross sections, it can, in some cases, be seen where these fibres 

 are continued across the cavity of the calyx to the cry stalline cone. It 

 is extremely difficult to prepare the crystalline cone in such a manner 

 that the radiating cross Striae can be seen. In some cases, the cones 

 remain perfectly transparent and apparently structureless ; in others, 

 one may succeed in detectìng the Striae, especially towards the inner 

 euds of the cones, which there appear to be less dense. In Pagurus^ 

 however , I have succeeded in obtaining- the clearest insight info the 

 structure of the crystalline cones. Here they are less hyaline, and the 

 Striae may be seen without special diffìculty. 



In ali these genera the pedicels are composed of two sets of plates. 

 the fibres in one of which are at right angles to those of the other. The 

 plates themselves appear to fit into each other in the same manner as 

 those of Penaeus. 



In the last named genus, the division of the corneal facets into 

 halves , produced by the Impression of the two underlying cells . was 

 so faintly marked that one might be tempted to doubt its meaning , if , 

 in other cases, there did not exist such positive evidence to the contrary. 

 In Galathea , the division of the facets is so plain , and corresponds so 

 exactly with the outlines of the corneal cells, that there can be no doubt 

 that the latter, and not the Krystallkegelzellen, as Grenacher believes, 

 give rise to the facets of the cornea. Indeed I have observed two instances 

 in which a facet was composed of two perfectly distinct parts, 

 each one of which corresponded with the underlying corneal cells 

 (PI. 31, fig. 116, a). In fig. 114, the divisions are represented as 

 extending from one angle of the facet to the opposite one. This how- 

 ever is very exceptional, for in by far the majority of cases it extends 

 from the middle of one wall, to a corresponding point in the opposite 

 one (fig. 116). This line of division, whatever its direction may be, 

 compared with the periphery of the facets , always lies directly over 

 the adjacent, median walls of the two corneal cells. 



