INVERTEBRATAj CRYPTOGAMIA, MICROSCOPY, ETC. 787 



Nervous System of Idotea entomon.* — This Isopod, selected 

 for study by M. Ed. Brandt, has three cephalic, seven tlioracico- 

 abdominal, and four post-abdominal nerve ganglia. Of the cephalic 

 group, the supra-oesophageal (not that so called by Rathke, which is 

 the sub-cesophageal) is made up of two median lobes, the hemispheres, 

 sending nerves to the interior antennse ; of two external, the optic, 

 lobes, giving off the optic nerves ; and of two antennary lobes supplying 

 the external antennaj. The short and very thick oesophageal collar 

 gives off two nerves to the labrum. The sub-oesophageal ganglion 

 is small, and, as in insects, gives off three nerve jiairs, to the labium, 

 maxillfe, and mandibles respectively. The third cephalic mass, for 

 which the name lyedomaxillary is proposed, rests on a special 

 pedomaxillary plate, and from it proceeds one pair of nerves, 

 similarly named, to the two maxillipedes. Of the ganglia of the 

 main body, the first is small, but larger than the pedomaxillary, and 

 all the rest arc of one size ; from each of them originates a nerve 

 pair to the feet, while the commissures between them supply the 

 muscles and integument of the segment. The pedomaxillary shows 

 the same arrangement, sending off nerves to the posterior part of the 

 head as well as those for the maxilliijedes. It would seem from its 

 innervation and the presence in it of a distinct ganglion that the 

 posterior part of the head is a thoracic segment amalgamated with 

 the head. The latter therefore forms part of an imperfect cephalo- 

 thorax, but is still morphologically different from the heads of insects. 

 The four post-abdominal ganglia are much smaller than those of 

 the body ; the three anterior are all of the same size, and give off" each 

 a single nerve pair to their segments ; the fourth is larger, and four 

 pairs of nerves proceed from it. An azygos sympathetic trunk lies 

 here between the commissural cords of the central system, and is 

 interrupted by ganglia as already described by F. Leydig in Purcellio 

 scaler. 



Cymothoidae. t — A year or two ago a request was sent to the 

 various museums of the world by Drs. Schiodte and Meinert, of 

 Copenhagen, requesting the loan of all specimens of Cymothoidfe 

 (Isopoda) for the pui-pose of monographing the group, and the first 

 portions of the monograph have now appeared. 



The first of these papers treats of the Cirolanidas, which closely 

 resemble the true Cymothoas, but which differ in having the mouth- 

 parts adapted for eating flesh. Three genera and nine species arc 

 characterized, of which the genera Baryhrotes and Tachaa, and species 

 B. iiulns, B. agilis, T. crassipes, CoraUana coUaris, brevipes, nodosa, 

 and hirsuta are new. Each species is described, as far as the specimens 

 permitted, under three heads — male, virgin, and ovigerous females — 

 the difference between the sexes and between the two forms of the 

 same sex being very striking. 



In the second paper the iEgidic are monographed. Those 

 Crustacea lead a parasitic life, generally attaching themselves to tlio 



♦ 'Coiuptcs Rcndus,' xc. (1880) p. 7i:5. 



t ' Nftt. Tiddsk.,' xii. pp. 21'.) nw\ .'J2I. Sro ' Am. Nat.,' xiv. (18S0) p. 510, 



3 F 2 



