THE EGGS OF CYCLOPIDES PALAEMON, ETC. 31 



view) that, with only one or two specimens to examine, it might readily 

 l»e overlooked. With C. silrius, it at once attracts attention on a careful 

 \iew. The difference when measurements are taken is not great, but 

 it is, nevertheless, very obvious to the eye. C. palaemun is decidedly 

 also the larger egg — its longest diameter being O-Slmm., that of 

 ('. silviuH being 0-72mm., the transverse diameters are respectively 

 0-72mm. and 0-68mm. The difference in each case being 0-09mm. 

 Tliis is, however, 12^ per cent, of the long diameter of ( '. nilriiis, and 

 under 11 per cent, of that of C. palaemon. The heights are: 

 ('. palaeiiKin =0-58m.i\i., C. silvi us = 0-50iniii. These are, however, 

 less reliable measurements than the others, the practical difficulties 

 of getting an exactly lateral vieAV of these rounded eggs being so 

 "great. 



In both, the micropylar depression is 0-1 5mm. across, and the 

 rosette about 0-03mm. The flattening at top looks wider than this on 

 a side view, the top being really a little flattened outside the depression 

 pi'oper. 



The sculpturing seems to be of identical character in both eggs, 

 but, in ('. palaeiiioii, the raised ribs are larger and thicker; they are, 

 however, even in ('. palaoiion, so slight and delicate, that it would be 

 more correct to say they are still slighter and more delicate in ('. silvins. 

 In a favourable light they can be seen with certainty round the 

 micropylar depression (in the living egg), and for a little way down 

 the outside slope ; lower down they seem to be absent. They form an 

 irregular polygonal network, nowhere definitely hexagonal, and with 

 the radial diameter of the cells longer than the circumferential. In 

 <'. palneiiion the diameter of the cells of the netting aa-e 0-03nim., 

 rather more or less according to which diameter is taken, and smaller 

 close up to the depression. The ribs are the merest threads as com- 

 pared with the size of the cells. In C. silvins the cells are fractionally 

 smaller. The cells are occupied by a pavement of dots or rounded 

 nodules, at least, they look so, but no elevations are seen on a profile 

 view ; these nodules continue of precisely the same character over the 

 lower part of the egg where no netting exists. In neither egg is there 

 the slightest trace of any upright ribbing. 



The annexed plates (plates ii and iii), from photographs by Mr. 

 F. N. Clark, will give a better idea of the sculpture and structure of 

 tliese eggs than prolonged description. Plate ii shows the micropjdar 

 ai'ea in C palaeiiinn magnified 250 diameters. The substance of the 

 egg-shell is so strong and solid that it cannot be flattened down 

 without various fractures, obvious enough in the plates. The pi. ii., 

 fig. 1, is focussed to the outer surface of the egg-shell, and shows very 

 well the micropylar rosette, and further out the polygonal network. 

 Plate ii., fig. 2, is precisely the same object, but viewed with the 

 focus set to the inner surface of the shell. The micropylar rosette 

 is less distinct, and the whole surface outside it is seen to be studded 

 with dots (raised points '?), arranged in an orderly but irregular 

 numner. The outer surface of the egg-shell, therefore, carries the 

 ribs; the inner is dedorated in this very different way. The dots 

 of the inner surface are, in their alignment, largely dominated by the 

 outside I'ibbing. Plate iii., fig. 1, is a similar portion of the egg 

 of C. silvins, the focussing being to the inner surface of the shell. 

 The cells of the micropylar area are, however, tolerably distinct. The 



