212 ME. STANLEY W. KEMP — BISCATAN PLANKTON : 



level of the adult. The evidence is, of course, far from conclusive and other records of 

 the post-larval forms throw no light on the subject. Coutiere's specimens were caught 

 in vertical nets at two stations, the hauls being 1000 m. to the surface and 3250 m. to 

 the surface ; those taken by the ' Helga ' oS tlie Irish coast were captured in a mid- 

 water otter-trawl, which was lowered to about 350 fathoms, the net fishing while being 

 hauled to the surface. 



Even in the case of the adult, a Macruran of almost world-wide distribution, but little 

 is known of the bathymetric range. The adult male present in this collection was caught 

 between 100 fathoms and the surface, a young male was caught off the American coast 

 actually on the surface, while the species has been trawled between 107 and 2949 

 fathoms. The probability, in the latter case, that the specimen was caught during the 

 ascent of the net renders it and similar records almost worthless from a bathymetric 

 point of view. The solution of the problem is to be sought either in successive hauls to 

 the surface from varying depths of wide- mouthed vertical nets, or, more certainly, by the 

 use of a self-closing net of very large dime as ions. 



AcANTHEPHTUA DEBiLis, A. Milnc-Edwards. 



A mature male, 67 mm. in length, was caught in haul 30 m, between 25 fathoms and 

 the surface. The basal crest of the rostrum bears four teeth, the rostrum itself being 

 furnished with twelve teeth above and eight below. 



The specimen, which is preserved in formalin, has retained a considerable amount of 

 the deep scarlet-red pigment so frequently met with among deep-sea Macrura, and the 

 numerous luminous spots and streaks so fully described by Couliere (Bull. Mus. Oceanogr 

 Monaco, No. 70, 1906) are well shown. The distribution of the red pigment in connection 

 with these presents features of some interest. Over each photopliore is seen a small 

 clear area, quite devoid of pigment, forming as it were a small window to allow of the 

 passage of light outwards. These transparent are areas of similar shape to the 

 photogenic spots over which they are placed ; over single round photophores they are 

 round, over the prominent vertical luminous organ which is situated behind the 5th pair 

 of thoracic legs there is a quite large elliptical area, while a narrow transparent line is to 

 be seen over the row of closely approximated photophores along the anterior basal edge 

 of the carapace. 



A. debilis is apparently a somewhat rare species and has been recorded from depths of 

 350 to 2512 fathoms. These captures were made with open nets and are consequently 

 of little value for the determination of the bathymetric range ; still it seems certain that 

 the present specimen was far above its normal horizon. 



The occasional appearance at the surface of species normally frequenting deep water 

 is a phenomenon of considerable interest. It has been suggested that the females rise to 

 the surface to liberate tlieir eggs in order that the larvai may have warmer water in 

 which to undergo their metamorphoses and a better chance of distribution by means of 

 ocean-currents. ] n the present species, however, the young leave the a^^ more fully 

 developed than is the case with A. purptirea, presumably that they may be enabled to 

 survive under conditions which would prove fatal to a zosea. 



