132 ON THE PLANKTON OF THE FAEROE CHANNEL. [Feb. 3, 



The same distribution was noted by Vallentin and Cunning- 

 ham 1 : " The adult, so far as our information allows of a 

 decision, lives on the bottom, and never swims far from the 

 ground [90-95 fathoms in this instance], while the young, up to 

 half or three-quarters the size of the adult, occur abundantly at 

 the very surface and at all intermediate depths. As mentioned 

 above, Mr. Murray found swarms of individuals at the surface in 

 the Faroe Channel, but none of these were full-grown, and very 

 few more than half the adult size." 



I have no doubt that this generalization will prove true for 

 greater depths : I took adult specimens, over 35 mm. in length, 

 only between 350-220 fathoms, 400-300 fathoms, 500-400 

 fathoms: the remaining specimens varied from 9 to 17 mm. in 

 length. In other words, Nyctiphanes norvegica is apparently 

 mesoplanktonic when adult. 



A few larvae, larger for their stage of development than those 

 attributed to Thysanoessa, were taken at the surface, and may 

 perhaps belong to Nyctiphanes : they have not been included in 

 the tables. 



THYSANOPODA MICROPHTHALMA Ortmann. (? = Thysanopoda 

 microphthalma G. 0. Sars.) 



Three specimens, recognizable as young forms by the character 

 of the second maxilla and gills, and by the spination of the telson, 

 of about eight, twelve, and fourteen mm. in length, appear to be 

 referable to the same species as specimens recorded in quantity 

 by the ' National ' in 60 3' N., 27 0' W., at a probable depth of 

 between 218 and 328 fathoms. These were referred by Ortmann 2 

 to Thysanopoda microphthalma of Sars 3 , a species founded on two 

 specimens from the surface at 26 21' N., 33 37' W., and 7 N., 

 23 W. respectively. The identity of the ' National ' specimens 

 with those described by Sars seems to me rather doubtful : firstly, 

 because it is not very likely that a rare form such as this should 

 occur as adult both at the surface near the Equator and also at 

 218-328 fathoms in the Greenland Sea, or at 500-400 fathoms 

 in the yet colder water of the Faeroe Channel ; secondly, because 

 Ortmann himself indicates some points of difference between his 

 specimens and those of Sars. My own specimens agree with 

 Ortmann's figure, and differ from Sars's description, in the shape 

 of the antennal scale, and in the absence of a spine from the 

 second joint of the first antenna. The telson was not hispid, 

 probably owing to immaturity ; the eye was somewhat flatter than 

 in Ortmann's figure, and showed slight signs of a constriction 

 such as is characteristic of Thysanoessa. The matter cannot be 

 settled in default of further specimens, owing to the fact that 

 Sars gave only a woodcut of the entire animal, and no figures of 

 the detailed anatomy. 



1 R. Vallentin & J. T. Cunningham : Quart. .Tourn. Micr. Sci. xxviii. pp. 325-6. 



2 A. Ortmann : ' Decapoden und Schizopoden der Plankton-Expedition,' p. 9. 



3 G. O. Sars : Chall. Rep. Zool., xiii. Schizopoda, p. 106. 



