262 Appendices to Sixth Annual Report 



on the other hand, like the Calanidae among the Copepoda, and the 

 Hyperiidae among the Amphipoda, pelagic in their habits. The phospho- 

 rescence of the sea is also apparently to some extent due to the power they 

 have — notably the species of theEuphausidae —of emitting light from various 

 parts of their bodies ; and it is a curious circumstance that it is those 

 species which have been observed to have preeminently the power of 

 becoming luminous that are most frequently found in the stomachs of 

 herrings, namely, Nyctiplianes and Boreophausia. Whether the property 

 of emitting light which these Schizopods possess has anything to do with 

 their being so commonly selected as food by the herring, cannot be easily 

 answered, though it is probable that their luminosity may have some 

 connection with it. 



The somewhat singular auditory organs observed in many of the 

 Mysidae are very interesting. They are conspicuous owing to their 

 glistening transparency ; they appear as clear circular vesicles near the 

 base of each of the inner caudal lamellae, which are at this part suddenly 

 enlarged to afford space for the vesicles. Viewed with a low power, each 

 vesicle appears to be formed of concentric zones or laminae, which are 

 alternately more and less clearly transparent; with a moderately high 

 power, the auditory ossicle may be observed. The position of the 

 auditory organs here referred to seems confined to the Mysidae. The 

 Cumaceae according to Claus do not possess auditory organs. 



The distribution of the Ostracoda, as might be expected from their 

 frequenting the mud, sea-weed, and zoophytes at the bottom, is, like that 

 of the Decapods, little influenced by the various seasons. The free- 

 swimming Copepoda are decidedly different in this respect. During the 

 later months of spring, and in summer and early autumn, they are at 

 times captured in great abundance by the surface-net ; whereas during the 

 colder months, comparatively few are to be met with, even though the net 

 be sunk to a considerable depth. In April and May I have also found 

 the larval or free-swimming forms of Balani exceedingly numerous — 

 much more so than at any other season. If adult Balani be collected 

 about this time, and left in sea-water for an hour or two, swarms of these 

 larval forms may be observed swimming about. It is probable that 

 during this time when the sea around our coasts is swarming with these 

 very minute organisms, the herring, and possibly other fishes also, may 

 make use of them as food, by drawing them into their mouths along with 

 the water of respiration, and retaining them while the water passes tu 

 through the opercula, as Dr Mobius suggested; but there is no doubt that 

 herring can, and do, discriminate between one form of food and another, and 

 purposely capture the organisms on which they generally feed, whether 

 Copepods, Amphipods, or Schizopods. 



The importance of this extensive class of organisms — perhaps the most 

 extensive among the Invertebrata — is a sufficient reason, if only from a 

 commercial point of view, for its being carefully and thoroughly studied. 



In the list here given, over 230 species of Crustacea are recorded 

 as occurring in the Firth of Forth, including 41 species of Ostracoda, 42 

 of Copepoda, and 13 Schizopods. 



In the list prepared by Leslie and Herdman, 99 species are enumerated ; 

 and Dr Henderson in his paper added other 21 species, which, including a 

 few doubtful forms, brought the total up to 120 species. The number of 

 species in the present list, exclusive of the two additional groups, Ostra- 

 coda and Copepoda, and leaving out doubtful forms, is about 150, which 

 shows that the investigations carried out during the pist year under the 

 directions of the Fishery Board have been fairly successful in adding to 

 our knowledge of the distribution of this important class of organisms. 



