REPORT ON THE CRUSTACEA MACRURA. 921 



the Sacculinidaa, and especially by the presence of two symmetrically situated apertures 

 (genital pores) at the ventral side, in the hindermost part of the body. 



In consequence perhaps of its being in the Norwegian language, this paper of M. Sars 

 has not become known so widely as it merited Neither Kossmann 1 nor Delate, 2 both 

 of whom give an extensive bibliography in their papers on the Rhizocephala, mentions the 

 above paper of M. Sars. 



In his second paper on the fauna of the Arctic fjords published in 1884, J. Sparre 

 Schneider of Troms0 3 gave an enumeration of the Crustaceans and Pycnogonids he 

 collected in 1881 in the Kvsenangsfjord. In this fjord Hippolyte pusiola is common at 

 a depth of 5 to 10 fathoms, at the place where it communicates with the Sdrfjord. 

 Schneider says 4 that this species is to a considerable degree infested with parasites, viz., 

 a species of Sylon peculiar to Hippolyte pusiola, a couple of them being often observed 

 on the same individual. 



In the same year Max Weber 5 published the results of his researches on the Isopods 

 collected during the cruises of the " WUlem Barents." Speaking oiPhryxus abdominalis 

 (Kroyer), Weber says 6 that along with the Isopoda of the Barents collection, a specimen 

 of Hippolyte incerta, Buchholz, was handed to him, which was infested on the ventral 

 surface by a parasite, that on superficial investigation might be taken for a Bopyrid. 

 On closer examination this idea was given up, and on comparing the parasite in question 

 with specimens of Sylon attached to Hippolyte pusiola, which he collected himself near 

 Tromsd, he saw at once that the parasite of Hippolyte incerta, Buchholz, also belonged 

 to the genus Sylon. Through the kindness of Professor Max Weber of Amsterdam 

 University, I was enabled to investigate two specimens of this species of Sylon, attached 

 to Hippolyte pusiola, Kroyer, and to compare them with the Challenger specimen obtained 

 off Halifax. This comparison brought out the great resemblance between them. They 

 may be different species, but they clearly both belong to the genus Sylon, Whether 

 in every case two specimens of Sylon living on different hosts should be regarded as 

 different species, I do not venture to decide. From the analogy of similar cases of 

 parasitical Isopoda, great prudence is certainly necessary in coming to a conclusion. 



1 Kossmann (Beitrjige zur Anatoinie der schmarotzenden Rankenfiissler, p. 5, 1874), says with regard to Sylon: — 

 " Der Genusname Sylon, welchen zu characterisiren Kroyer durch den Tod gehindert wurde, kann fuglich aus unserer 

 Literatur ivieder verschwinden, zumal K. seine Exemplare, wie er selbst angibt, sarnnitlich verarbeitet hat." 



2 Delage (Evolution de la Sacculine, Archives d. Zool. expe'r. (2), torn. ii. p. 424, 1884), in regard to Sylon is also very 

 decided : — " La meme annee (1855) Kroyer ajoute aux deux genres deja connus le genre Sylon. Mais il omet de le carac- 

 teriser et de conserver un exemplaire. Personne depuis n'a pu retrouver le Sylon, en sorte que c'est la un genre, que 

 sauf Kroyer, personne n'a vu, et dont personne ne connatt les caracteres. Le retrouvera-t-on '." 



3 J. Sparre Schneider, Unders0gelser af dyrelivet i de Arktiske fjorde, II. Crustacea og Pycnogonida indsamlede 

 i Kvaenangsfjorden, 1881, Tromsij) Museums Aarshefter, vii., 1884 



4 Loc. cit., p. 52. 



6 Max Weber, Die Isopoden gesammelt wa'hrend der Farhten des "Willem Barents" in das Nordliche Eismeer in 

 den Jahren 1880 und 1881, Bijdragen tot de Dierhmde, 1884. 

 6 Loc. cit, p. 34. 

 (zool. CHALL. EXP. PART LII. 1888.) Fff 116 



