1638 THE VOYAGE OF H.M.S. CHALLENGER. 



the former is strikingly flattened out : on the other hand, Pereionotus tesludo (Montagu) 

 and Icridium fuscum, Grube, which come very near to Guenn's species, agree ■with 

 Iphigenia typica in having the 'depressed Isopod-like body ; the maxillipeds of Icridium 

 fmctim are said to have a three-jointed palp, agreeing in this respect with the maxillipeds 

 figured by Mr. Thomson for his species, but not agreeing with a specimen of Iphigenia 

 typica sent me by Mr. Chilton, in which the maxilliped-palps are four-jointed ; the 

 mandibles in this specimen agree with those which Grube describes, in having four teeth 

 to the cutting edge and no visible palp; in regard to the pleon Grube's species is very 

 distinct from Thomson's; until, however, the mouth organs of the genera referred to 

 have been more fully described and figured, and the anomalous character of the pleon in 

 Grube's Icridium has been either established or disproved, the relation of these remarkable 

 forms to one another must remain very uncertain. 



1883. Graeffe, Ed. 



Biologische Notizen iiber Seethiere der Adria. Ueber die Fauna der Schlamm- 

 region der Adria. Bolletino della Societa adriatica di scienze uaturali in Trieste. 

 Volume ottavo. Trieste, 1883. pp. 85-89. 



The two species of Amphipods recorded from this mud-region are " Ampelisca Gaimardi Kroyer," 

 and " Phoxus plumosus Kroyer." Professor Graeffe regards these two species as strongly 

 supporting his view that the mud-dwellers have suffered degradation of the visual organs 

 owing to the character of their habitat. 



" The Crevettines or Gammaridse," be says, " to which division these Amphipods belong, 

 generally exhibit sessile eyes, that is, the pair of eyes is situated wholly in the cephalo- 

 thorax. A part of the chitin-layer of this is bulged out, and provided with facets, which 

 are more or less clearly developed. Behind this facetted corneal-surfaco there is a pigment- 

 layer, which envelops the elements of the arthropod- eye, crystal-cone, and rhabdom-layer of 

 the retina. The optic-nerves which provide for this eye, are derived from a special cerebral- 

 knot or ganglion. 



" In Ampelisca this corneal-part of the eye is only provided with two facets, which points to an 

 arrested development of it, as these facets, to which the refracting and sentient retina-rods 

 correspond in number are multiplied with the development, the growth of the animal. In 

 Ampelisca Gaimardi, moreover, the pigment of the eye is little developed, so that one may 

 well maintain that this species possesses a degraded pair of eyes. 



" In Phoxus plumosus this degradation has advanced still further, since here no corneal part 

 whatever is to be seen, and in the place of the eye there is only a faint yellowish pigment- 

 fleck remaining. This species is to be reckoned among the totally blind animals." 



On the subject of the eyes in Ampelisca, see Note on Leila Valle, 1888 (p. 1651). 



1883. Herrmann, G. 



Sur la spermatogenese chez les Crustace's e"driophthalmes. In Compt. Rend. 



Tome 97. pp. 1008-1012. Also in Journ. Micr. Paris. Annexe 7. pp. 588-590. 



According to this author " verliiuft die Spermatogenese bei Ligia, Idotca, Sphxroma, Gammarus, 

 Talitrus in ganz anderer Art als bei den Podophthalmen und erinnert bis auf das sehr friihe 

 Verschwinden des ' nodule cephalique ' in auffallender Weise an die der Selachier. Das 

 Spermatozoid bleibt unbeweglich (vergl. Bericht f. 1879. p. 418 u. 1882. II. p. 21)." 

 Zool, Jahresbericht fur 1883. 



