ISO 



Part III. — Fifteenth Annual lieport 



Larva} of this second class are in reality in an unhealthy condition, and I 

 have never found any food in their stomachs. 



I am not yet certain, but there is reason to think that these two classes 

 of larvae in reality had been starving while in the hatching apparatus, 

 where they perhaps were retained rather long. 



(3) The third class of fry in the rearing jar formed the minority ; they 

 had a healthy appearance, and were richly pigmented. They were seen 

 at all levels, as a rule swimming slowly, and were always looking for 

 food. This they did so intently that hardly any object in the water was 

 passed unobserved. 



Tenth to Fifteenth day after Hatching. 



Though appearing at all parts of the jar, these feeding larvai were chiefly 

 found in places where the living food most accumulated, viz. : at the side 

 nearest the w ndow, where the light was strongest. The food, as men- 

 tioned, consisted of tow-net collections from the surface of the harbour, 

 taken at all states of the tide. These collections varied in richness, ac- 

 cording to the weather, but I never failed to get multitudes of diatoms, 

 larval and adult crustaceans (chiefly copepoda), and larval mollusks, etc. 



Although the feeding fry pay attention to perhaps anything suspended 

 in the water, living or dead, only few forms were eaten at the time. The 

 first food found in their stomachs was as follows : — (1) Diatoms {Guin- 

 ardia ftaccidd), a commonly occurring form ; (2) A small larval mollusk 

 (Buccinuml), measuring 0*16 mm. in length and 0*112 mm. in breadth 

 (PI. I. fig. 11). The mollusk was found three or four times more frequently 

 than the diatoms, and it is noteworthy that I in no case found both forms 

 in the same specimen at the same time. However well filled the stomach 

 was, its contents in this earliest post- larval stage were almost without excep- 

 tion one thing only. It seemed as if the young fish had become familiar 

 with one particular kind of food, and took that alone for some time. But 

 as different individuals fix upon different forms, there is no reason to 

 conclude that one kind of food alone was of vital importance. 



The larval stage of the plaice (from the time of hatching till the yolk 

 is absorbed)* has been described by several authors ; M'Intosh and 

 Prince,f Cunningham, \ Fullarton,§ Ehrenbaum,|| and others. 



There is some difference between the various authors in respect to the 

 size of the plaice at the end of the larval stage, due no doubt to the varia- 

 tion in the size of the egg, and my observations are in near correspond- 

 ance with those of Ebenbaum ; he gives the average size at the end of 

 the larval stage as 7*5 mm., or slightly more ; while I have found the 

 average size of this stage to be 7*2 mm., while specimens are frequently 

 found that measure 7 '5 mm. 



expressed the same view with reference to larval turbot [F. B 13th An. Rep., Part 

 III., page 229]. This appears to be the case during the first few days of the post- 

 larval stage, to which the experiments were confined ; but I now doubt whether 

 this somewhat artificially produced activity will ever prove beneficial to the 

 rearing fry. 



* "While Cunningham, and lately Ehrenbaum, apply the term 1 larvre ' to the 

 young fish, from the moment of hatching till it has acquired the form and habit of 

 the adult, M'Intosh has divided this period into two stages — the larval, from hatch- 

 ing till the absorption of the yolk is completed, and post-larval, from this time till 

 the adult form appears. The latter is at least the most definite, and has been 

 followed in this paper. 



t Trans. Roy. Soc. Edin., vol. xxxv. part iii., 1887-88, p. 840. 



+ Trans. Roy. Soc. Edin., vol. xxxiii. parti., 1887, p. 92. 



§ Ninth Annual Report of Fishery Board, part iii. 1890, p. 311. 



II Eier und Larven von Fischen der deutschen Bucht. Keil and Leipzig, 1897. 



