REPORT ON THE AMPHIPODA. 449 



agreement with Leyilig and contrary to the view of Speuce Bate, as organs of smell. The 

 fact that they are longer in the blind Gammanis puteanns and AseUiis from the wells than 

 in Gammanis pulex and Asellus aquaticus is regarded as a natural compensation made to the 

 former for their want of sight. To the plumose hairs at the base of the upper antennae, 

 which Sars and others accept as auditory organs, like those described by Hensen for the 

 Decapods, Eougemont disallows this function, on the ground that to the well- and cave- 

 shrimps hearing would be of no particular service, and that in Amphipods neither auditory 

 vesicle nor otolith has been discovered. He regards the hairs in question as ministering to 

 the sense of touch, and were there any word to express something intermediate between the 

 senses of touch and hearing, he would be willing to adopt it for the function of these 

 organs. He agrees with some earlier writers in ascribing to the cone of the antennary gland a 

 sense of smell, and supposes, while the cylinders of the tlagellum smell more distant objects, the 

 cone takes cognizance of food approaching the mouth, an ingenious but not highly probable 



' suggestion. He mentions that Felix Plateau, who like Spence Bate recognised eyes in Gam- 

 marus puteanus, briefly described these organs as "dreieckig mit spharischen Winkeln, 

 klein und pigmeutlos." But de Eougemont himself had never been able to find any 

 Krystallkorperchen, and is convinced that these animals cannot see and distinguish objects, 

 though the light, penetrating their transparent skin to the rudiment of the optic nerve, may 

 produce a disagreeable impression, whicli leads them to prefer a safe obscurity. 



To the single species, Gammarus puteanus, Koch, are referred all the following forms: — I. Form. 

 Gammanis minutus, Gervais. Crangonyx subterraneus, Sp. Bate. II. Form. Niphargus 

 Jcochianus, Sp. Bate. III. Form. Gammarus puteanus, Caspari. Gammarus puteanus. 

 Hosius. Nipihanjus fontanus, B'p.'^a&B. lY.'EoTim. Gammarus puteanus, Yi.oc\i. V. Form. 

 Niphargus stygius, Schiodte. Gammarus pideanus, Koch, de Lavalette St. George, and Felix 

 Plateau. VI. Form. A colossal specimen, 33 mm. long, from Neuchatel. These identifica- 

 tions were sharply criticised by Alois Humbert, in 1876. 



1875. SCHI0DTE, J. C. 



Krebsdyrenes Sugemiiiid. Med fern Kobbertavler. Naturhistorisk Tidsskrift 

 3. R. 10. B. Kj0benliavii. 1875. pp. 211-252. 



Schi0dte considers that the structure of the mouth in the Amjjhipoda offers three princijiul 

 types, best distinguished by the connections which determine the movements of the 

 mandibles. The first type belongs to the Gaiirmarus- Caprella-iorms. Here the mandibles 

 are short, three-sided, with broad triangular base, the outer angle of which is socketed by 

 a short process in the pleural border of the head. On this process and the outer side of 

 the shaft they have an oscillating movement, but being free from the special arrangements 

 for regulating their movements which are found in the other two types, he calls this 

 group Eleutherognatha, defined by the formula, " Mandihulx trigonal, conchjlo articulario 

 anticd carentes. Lahruin pjlnniusculum, fransversuin, simp}le.i\" The lower lip he describes 

 as having four comparatively soft cushion-like lobes and two more strongly chitinized and 

 calcified horns directed backwards, stifTer than the cushions, yet yielding towards their 

 free ends, so as to constitute a spring stiff enough to hold the mandibles up for their 

 oscillation, yet elastic enough to yield to pressure, and which he therefore designates as 

 '' ptrocessus mandihularii lahii inferioris." 



The second type includes most of the Lysianassina, Dana. Here, in addition to the arrange- 

 ments above mentioned, " from the front end of the shaft, on the upper side, in front of 

 the palp, there issues a club-shaped, articular process, rounded at the end, which fits into a 

 corresponding cup on either side of a .saddle-shaped process on the palate, close behind 



(ZOOL. CHALL. EXP. — PART LXVIL — 1887.) XxX 57 



