248 M. A. Humbert on Nipliargus puteanus, var. Forelii. 



In my memoir there will be found a very detailed descrip- 

 tion of the species, founded upon the examination of a great 

 number of specimens, which M. Forel had the kindness to 

 furnish me with. I hope I have thus brought out characters 

 derived from organs which are often too much neglected, at 

 the same time avoiding the mention as specific of purely 

 individual peculiarities. I shall content myself here with in- 

 dicating some points in the organization of these crustaceans 

 which seem to me more particularly to deserve the attention 

 of anatomists. 



Of the authors who have treated of the species of the genus 

 Nvphargus^ some say positively that the eyes are deficient ; 

 others that they are without pigment and not apparent, which 

 is as much as to say that they have not perceived them ; 

 others, again, describe them as yellow or as imperfectly formed. 

 M. Plateau asserts that they exist, but are destitute of pig- 

 ment. It appears, however, from his memoir that he did not 

 see them, and only convinced himself of their existence by 

 physiological experiments, which proved to him that the 

 Niphargi were sensible of light. M. de Rougemont saw 

 some irregular pigment-spots on the sides of the head ; but he 

 does not believe in the presence of an optical apparatus. For 

 my own part, I have been unable to perceive the least trace of 

 eyes or even of a deposit of pigment. 



M. de la Valette-Saint-George described and figured some 

 very small organs situated on the dorsal parts of the seg- 

 ments, and composed of a small capsule, from which issues a 

 filament which bifurcates. I have examined these singular 

 organs, to which I have given the name of sensitive capsulesy 

 in rather more detail, and ascertained that they occur not only 

 on the segments, but also along the anterior margin of the 

 head and on the first two joints of the peduncle of the superior 

 antennae. The capsule, placed beneath the chitinous enve- 

 lope, is ovoidal, delicate, transparent, and open at both its 

 poles. Through the exterior orifice issues a hyaline and 

 homogeneous filament, which is straight for the greater part of 

 its length, but is curved towards the end and has its extremity 

 obliquely truncated. A fine dark line, probably indicating a 

 furrow, commences near its origin, and runs as far as its distal 

 extremity. At about ^ of the length of the filament (that is 

 to say, at the point where it begins to bend) a much finer fila- 

 ment detaches itself from the former, on the convex side of 

 the curvature, at an acute angle. This secondary filament, 

 which is very thin at its origin, soon becomes excessively 

 slender and sometimes difficult to follow. Its length some- 

 what exceeds that of the principal filament. Sometimes only 

 the parts that I have just described exist j but in other cases, 



