88 Dr. 0. Grimm on some Blind 



appears to be the case with the large, gibbose, dark eyes of 

 Caspian Mysidas, of Gammar acanthus caspius^ the species of 

 Boeckia, &c. It is, however, conceivable that in many 

 animals in the persistent darkness the eyes do not become 

 developed and are replaced by other organs of sense. In the 

 latter case the eyes may even become degenerated, and the 

 more rapidly and completely the less they are nsed, the less 

 the service they render or are capable of rendering to their 

 possessor. We may take as examples Niphargus caspius* 

 and the above-mentioned species of Onesimus. 



In examining these we find highly developed sense-organs, 

 which probably function not only as organs of touch, but also 

 (at least in the species of Onesimus) as organs of taste f. 



Besides small, but dark-pigmented eyes, which can probably 

 hardly function at depths of 35-90 fathoms, and which must 

 be regarded as the remains of eyes which formerly functioned, 

 Niphargus caspius has exceedingly well-developed organs of 

 smell and touch on the antennae, and especially on the upper 

 ones. At the same time it is to be remarked that the males, 

 which have the smaller eyes, possess a greater number of these 

 sense-organs than the females, which, with respect to other 

 characters also, e. g. the number of joints in the secondary 



* From this species N. puteanus is probably derived. It is possible 

 that it is identical "with N. ponticus, Czern. $ unfortunately I have been 

 unable rightly to determine the latter, as the description which M. W. 

 Czernjewsky has given of it appears to be very defective. (See his 

 ' Materialia ad monographiam ponticam comparatam.') It must, how- 

 ever, be remarked that our JV! caspius differs in many respects from the 

 other species of Niphargus, and, indeed, from N. puteanus, as in its shorter 

 antenna?, the differently formed hand of the last pair of limbs, &c. ; so 

 that, perhaps, our species may be regarded as the representative of a new 

 genus between Niphargus and Gammarus. 1 do not take this course, 

 however, and recognize in the different organization of M. jmteanus the 

 expression of a further development under the influence of certain condi- 

 tions, which have superinduced the deficiency of the eyes and, at the 

 same time, the greater development of the antennas which bear the sense- 

 organs that take the place of the eyes. In any case, Niphargus caspius 

 appears to be the older form, which has maintained itself (perhaps some- 

 what altered) in the Caspian down to the present time, just as other 

 species of the Tertiary period still continue to exist there, as I have 

 indicated in my ' Kaspischen Fauna,' Lief, ii., in the case of Dreissena 

 rodrifoi mis, D. Brardii, I). caspia, Cardium catillus, Phinorlis microm- 

 phalus, &c. Niphargus caspivs is very probably the " extinct Gam- 

 marid " (see Leydig, "Ueber Amphipoden und Isopoden," Zeitschr. f. 

 wiss. Zool. xxx. p. 249) which the other species of Niphargus have as 

 their ancestor. 



t In many cases, no doubt, it is difficult to decide whether a certain 

 organ is adapted to feeling, tasting, or hearing ; nay, it is exceedingly 

 probable that in many of the lower animals the faculty of touch is not 

 separated from taste and hearing. 



