422 PROCEEDTNGS OF THE NATIONAL MUSEUM. 



godes, where the loss of eyes is not always ai-companieil l)y other change-'^ in funii 

 and structure, and so with other cases. 



If we turn to the European Asellus forrlil Blanc, a l)lin(l species from tlie al)ysses 

 of Lake Leman, we see that it does not belong to our genus Cu-cidolcii, although it has 

 been referred to Circidoteu ])y Fuchs in his i>aper f)n tlie fauna of the deep sea. 

 Asellus forelii, compared with s]K'ciniens of Axellux ikjhiiUciis from Belgium, is about 

 half as long and broad as .1. iK/ddlirnn; the body lias retained about the same pro- 

 portions; the telson (abdomen) is little, if any, narrower or elongated. Both 

 branches of the caudal stylets are of about the same lengtli as in .1. miKiilicus. Asel- 

 liiK forelii, then, appears to us to be evidently a depau])erated species, closely allied 

 \.) A. <(/j(i<tticitx, which has lost its eyes by its life in supposed i)erpetual darkness at 

 oi- near the l)ottoni of Lake Geneva. Its generic characters are identical with those 

 of its parent form, A. (KjKdficm^. So also are those of .1. fdraticus SchiixUe, found in 

 wells in Germany, and which closely resembles A. J'on'/ti, only differing in slight 

 specific I'haracters. It is evident that these two blind species were originally derived 

 from A. aquatlcus, and hence have retained the generic characters and specific marks 

 of that European species as compared with our American .1. nriiiiuiitiis. 



When, however, we turn to our ('ncidntin slijijid an<l iiickn/Kfl-ciisis, we lind that 

 they are not only not congeners of the l)lind Eurojiean Asclli, but that tliey are also 

 not congeneric witli the American Asellus communis, and tl>at there are no interme- 

 diate forms connecting them, although the eyed species of AseUnx are somewliat 

 variable. Hence, we feel warranted, on taxonomic groumls, whatever may be our 

 theory about their origin, to retain the genus Ca'ddoteu. 



Since the above was written, throe species of Asellus liave Itocn 

 described, Aselh/s hopplmv Garman, Asellus tnnndetis/s Harford, and 

 Asellus atteniiatus Richardson; the former from southwestern Mis- 

 souri, the second from California, and the hitter from the Dismal 

 Swamp. There is prol)al)ly still another species, as 3'et iindescrilx'd, 

 which occurs in the District of Columbia. The Southern States have 

 been very poorly explored for their fresh-water crustacean fauna, and 

 there can be no dou])t that Avhen the work is undertaken many addi- 

 tional species of Asellus will be ])roug-ht to liolit. They, therefore, 

 are more abundant than Packard supposed, and exist, prolnibly, as 

 distinct species in nearly every cave region. 



Dr. Packard's claim "that the two or three species of ^ Canildotea' 

 are cono-oneric among- themselves on one hand and g-enerically dis- 

 tinct from the genus Asellus on the other," is a statement \vhich we 

 could understand had he not followed it up with the statement that ''the 

 species have probably arisen independently."''' A genus, according to 

 the usual conception, is a natural aggregation of .species and not a het- 

 erogeneous assemblage of species, grouped together simpl}^ because 

 the}' happen to resemble each other. That such heterogeneous genera 

 do exist and are accepted is quite probable, but they are accepted 

 because we know nothing more of the animals than that the}' look alike. 

 The genus Csecldotea presents a case in which, in spite of the lack of 

 good generic character and the very strong prohal)ility — one might 

 almost .say certainty — that the species are not of similar origin, carcm- 

 ologists have been willing to group them together. In this connection 

 we are strongly reminded of the ett'ort of Cope to establish the genus 



