of the Fishery Board for Scotland. 



15 



authors at different times maintaining that they are specifically 

 the same, a circumstance attributed to only a few specimens having 

 been examined, and the specific characters as published ambiguous. 

 By a study of the distinguishing characters and numerous measure- 

 ments, Dr. Williamson shows that these two species are distinct, 

 and a key is given incorporating the results of the previous and 

 the present researches, by which the six species may be separated. 

 The same naturalist supplies a paper, with two plates of drawings, 

 on hermaphroditism in the cod, a condition which is normal in 

 certain fishes, as the Gilthead (Chrysophrys auratus), and occurs 

 occasionally in others. 



The Otoliths or Earstones of Fishes. 



In this Keport will be found a long and elaborate paper by Dr. 

 Thomas Scott on the otoliths or earstones of teleostean or bony 

 fishes, which is illustrated by five plates containing figures of the 

 otoliths described, belonging to about seventy species. The 

 otoliths of different fishes vary remarkably in shape and size, 

 and Dr. Scott shows how these differences may be used as a means 

 for the identification of the various species should other data not be 

 available. It is thus sometimes possible, as the author has shown 

 in previous papers, to tell upon what fishes a particular fish or ceta- 

 cean may have been feeding, by the presence of the earstones alone. 

 The otoliths consist almost entirely of calcareous matter, only a trace 

 of organic tissue being present. The structure shows that the limy 

 matter is deposited in concentric layers, the density of each layer 

 being slightly greater or less than the one immediately preceding 

 it. In flat fishes, the earstones form round or oval discs, so thin 

 that the alternating concentric layers are easily made out. The 

 number of such layers, or growth-lines, appears to correspond more 

 or less closely with the age of the fish, but Dr. Scott is of opinion 

 from his researches that it is doubtful if the evidence of age 

 obtained in this way can be safely relied on. 



The same naturalist also contributes a brief paper on new and 

 rare copepoda from the Scottish seas, illustrated by a plate of 

 drawings. Most of the species were obtained in the Firth of Forth 

 and the Moray Firth. 



The Spawning and Fecundity of the Plaice. 



An experiment was made on this subject by Dr. Fulton, by 

 keeping adult plaice about to spawn in tanks and collecting all the 

 eggs that appeared in the overflow daily, or twice daily. By this 

 means the number of eggs spawned by each of the two females 

 experimented with was determined, as well as the duration of the 

 spawning and the quantity of eggs that appeared from day to day. 

 One of the females spawned steadily, and almost daily for a neriod 

 of 36 days, the quantity shed at any time being small ; the 

 spawning of the other extended over 41 days, but eggs were 

 spawned on only 16 days during the period, large quantities of 

 eggs being shed on each occasion, as many as 49,000. The first 



