648 William Patten 



of the calyx are fìnely strip ed , as though covered with quite regularly 

 arranged fibres (fig. 118), 



The calyx is divided into four Chambers by the inner walls of the 

 four retinophorae (fig. 119); near its inner end two of the walls dis- 

 appear, and consequently the retinidium is divided intohalves, the piane 

 of division passingthroughthetwopigmentedcells,jo^.3 (fig. 121). Finally 

 these walls also disappear, at that point where the calyx is trausformed 

 into the style (fig. 122). Although the axial walls of the retinophorae 

 have disappeared, the abaxial ones, which form the calyx, continue as 

 a closed and narrow tube, the style, as far as the basai membrane. The 

 same method of Innervation is to be found bere as in the Mollusca and 

 Crustacea ; each celi is provided with a number of nerve fibres, exteuding 

 its wholelength, and closely applied to its outer surface. By the 

 concrescence of the retinophorae, the nerve fibres of the adjacent walls 

 did not disappear, but carne to lie in the centre of the group ; as the union 

 became more intimate, theinner walls disappeared entirely, and the nerve 

 fibres became as completely enclosed by the united celi walls as though 

 they had developed within a single celi. With a good oil immersion, it 

 may be seen, without special difficulty, inproperlyprepared material, that 

 the axial bündle of nerve fibres thus formed occupies the centres of the 

 narrow tubes produced by the united stalks of the four retinophorae 

 (fig. 128). The conditions for Observation are so unfavorable at the 

 inner end of the style, that the narrow tube with its centrai fibre is with 

 difficulty distinguishable ; but at the outer end, the tube is considerably 

 enlarged , and the axial nerve bündle is seen to consist of four distinct 

 fibres , which themselves are probably composed of numerous smaller 

 ones (fig. 124). Just beyond the narrow neck of the calyx (fig. 128), 

 the four bundles of nerve fibres break up into innumerable branches, 

 which follow the median partition for a short distance and then separate 

 to form four groups , each one of which passes through the middle of 

 one of the four Chambers of the calyx (figs. 121 and 119). From each 

 of these fibres, are given off innumerable horizontal fi bril- 

 lae, which fuse and interlace with each other to form a com- 

 plete nervous network, distinguishable only in the most 

 carefully prepared material. The best method of preparation is 

 the one I have already described for Pecten, i. e. treatment for about 

 half an hour in chromic acid, VsVo^ ^t 45» Centigrade. The following 

 day, one may pick to pieces with needles, and examine in acetate of 

 potash. By this method, the most beautiful results are obtained, for it 

 very often happens that the whole retinidium may be isolated 



