INVERTEBRATA, CRYPTOQAMIA, MICROSCOPY, ETC. 71 



iuterspaces between the front and the internal suborbital lobes. The 

 third joint of the external maxillipedes with an obtuse-angled emargi- 

 nation in its anterior border ; the three terminal joints, however, fully 

 visible externally when the maxillipedes are properly closed, the latter 

 having quite the same shape and form as in Pelocarcinus Lalandei 

 M. Edw. This genus evidently presents a remarkable transition from 

 Pelocarcinus M. Edw. to Hylceocarcinus Wood-Mason, as the latter 

 genus is intermediate between Pelocarcinus and Gecarcinus. 



Malacosoma is a new genus of the Pinuotheridaj. It has the 

 characteristic physiognomy of Pinnotheres, but it differs by the struc- 

 ture of the external maxillipedes. The second joint (ischiognathite 

 M. Edw.) is rectangular, and but a little longer than broad ; the 

 third joint (merognathite M. Edw.) is quadrangular, shorter than the 

 second, and the terminal joints are affixed to its internal angle. The 

 internal margins of the second and third joints of the external maxilli- 

 pedes are straight, and consequently the two maxillipedes are lying close 

 to each other. The exopodites (exognathe M. Edw.) of these outer 

 foot-jaws are stout, and almost half as broad as the third joint. The 

 integument is as weak as in Pinnotheres, and therefore it is possible 

 that Malacosoma has also the same manner of life as the crustaceans 

 belonging to the group of Pinnotheres. 



Mypsilograpsus has its external maxillipedes similar to those of 

 Gnathograpsus Alph. M. Edw., but it may be distinguished by the 

 very thick body, the very convex carapace, and the very deflexed front. 

 In these points it differs too much from Gnathograpsus to be ranged 

 in that genus. 



Change in Colour in the Isopoda.* — Dr. Mayer gives a short 

 account of his observations on some species of Idothea, in which this 

 change in coloration is so well max'ked. He says that if two equally 

 brown specimens are taken, and one is placed in a black and one in 

 a white vessel, there is, within half an hour, a marked difference 

 between them, so that while the white one is hardly to be distinguished 

 from the vessel, the brown one will have become quite dark. When 

 one eye is extirpated, the animal operated on may still change its 

 colour ; but if hath are removed, the creature never exhibits this power. 

 These experiments are in support of the ali'eady enunciated views of 

 Pouchet and Jourdain. 



Blind Isopod from the Lake of Geneva, t — The Isopod, Ascllus 

 Forelii, described by M. Blanc, is, as might have been expected, found at 

 a distance from the light, viz. at from 75 to 300 metres below the surface, 

 and is interesting by way of comparison with the other blind Crustacea 

 which have lately attracted so much attention, as it has been confounded 

 hitherto with one of these, Ascllus Sicboldii, or with A. cavaticus. It 

 also much resembles A. aqiiaticus. Its length is 5 mm. as against 8 mm. 

 of A. cavaticus. Its antenna) also exhibit flagella of four to live joints, 

 the second pair having never more than twenty-six. The thorax agrees 

 with that of A. cavaticus in form, also the thoracic limbs. Of tho 

 abdominal limbs, the first in the male is slightly smaller and less 



♦ Loc. cit., p. 521. t ' Bull. Soc. Viiud. Sci. Nat.,' xvi. (187'J) p. 377, 



