M. A. Humbert oti Niphargiis puteanus, var. Forelii. 245 



A^. sfi/fjnis of Scliiiidtc aiul the A. puteanus of Koch. To 

 tlicse live forni.s observed at ]\Iunicli, M. de liouf^eniont adds a 

 sixtli found in a wcdl at Neuehatel, and measuring 33 millims. 

 in length. Besides its colossal dimensions, the specimen from 

 Neuchdtel is distinguished by a considerable number of joints 

 (51) in the superior antennje, and by the almost complete dis- 

 appearance of the accessory flagellum, which only shows 

 itself in the form of a mere spine. 



It is to be regretted that the author, who has himself dredged 

 Xiphair/i in the lake of Neuehatel, does not tell us whether 

 these Crustaceans fall under any one of the six forms which 

 he establishes for the Gammarida of the wells. 



M. de Kougemont was struck with the discovery in a single 

 well of live different forms, and found it difficult to believe 

 that five species so nearly allied to each other should live 

 together in so limited a s])ace. He sought in vain for small 

 specimens representing the young condition of the larger 

 forms. Out of about a hundred individuals he found none of 

 the dimensions of 2-4 millims. which approximated to the 

 form which attains IS millims. He then asked himself, whence 

 came these large individuals ? and he arrived at the conclusion 

 that these five forms are not species, but only diti'erent stages 

 of development of one and the same species, namely Gammarus 

 vuteanus, Koch. 



Thus, according to him, something of the same kind would 

 take place here as in the case of the salmons, which, when 

 they are not more than (3 inches long, already present com- 

 pletely developed reproductive organs and nevertheless con- 

 tinue to grow until they attain a length of 5 feet. In the 

 Gamman, as in the salmons, characteristic forms would seem 

 to make their appearance as the animal increases in age. 

 This naturalist isolated certain forms, with the object of 

 ascertaining whether they really underwent metamorphoses. 

 His experiment was successful. He saw individuals pass by 

 change of skin from the first form {Crangonyx suhterraneus) 

 to the second (Xiphargus Kochiamis) ; and he also observed 

 the transformation of the fourth form into the fifth. Hence 

 the author concludes that the genera Crangonyx and Niphar- 

 gus must not be separated, since they only represent diti'erent 

 states of one and the same sj)ecies. He goes even further, 

 and proposes the suppression of the genus Xij)ha)-gus, which 

 he regards as being nothing more than the result of a modifi- 

 cation of Gammarus pulex. 



The facts upon which M. de Rougemont relies are doubtless 

 very curious and of much significance. It cannot be denied 

 that we have in them observations worthy of tiie utmost atten- 

 tion on the part of zoologists. I think, however, that we 



