St. Andretos Marine Laboratory. 303 



posteriorly to the fundus of the sac, its tissue insinuating 

 itself between the yolk and its proper covering and the yolk- 

 sac. The rounded gall-bladder lies at the posterior and upper 

 region of the latter, and after the absorption of most of the 

 yolk and the consequent forward displacement of the oil- 

 globule this large sac remained very conspicuous. The ali- 

 mentary canal in the advanced forms presents two marked 

 constrictions, one behind the gall-bladder and another a little 

 in front of the anus, which occurs near the middle of the body, 

 a feature, after absorption of the yolk-sac, that at once dis- 

 tinguishes them from the larval herring, in which the anus 

 lies very far back. The conspicuous gall-bladder is also 

 diagnostic when compared with the larval sand-eel, in which 

 the anus is likewise more or less median in position. 



4. General Remarks on Post-larval Food-Fishes. 



There seems to be a community in habit amongst the post- 

 larval Gadoids, especially, so far as present knowledge goes, in 

 the case of the cod and whiting, though probably also in the 

 haddock, just as there is a community in regard to their ova. 

 In the early post-larval stages of the cod and whiting close 

 resemblances exist, especially after preservation in spirit, but 

 they are easily discriminated after reaching the length of 

 about five eighths of an inch. They roam throughout the 

 deeper parts of the neighbouring sea, but are not confined 

 thereto, some being occasionally found in the upper regions 

 and some in the shallow water (4-5 fathoms). They are met 

 with, however, in greatest numbers in the regions near the 

 bottom in their post-larval stages. 



It is doubtful if the migrations described by Prof. G. O. 

 Sars in the case of the cod can, in the light of present facts, 

 be accepted as the rule in this or in allied species. The 

 floating eggs are carried (if they are not already there) into 

 shallow as well as into deep water, and thus the post-larval 

 fishes are common in both regions. Most, however, probably 

 occur on or near the grounds frequented by the adults, and 

 hence it is that far from shore young post-larval forms are 

 even more numerous than in shallow or other water near 

 land. The same applies to certain flat fishes, such as the 

 witch [Pleuronectes cynoglossus)^ the young of which keep 

 near the ground frequented by the adult and do not migrate 

 to any extent into other regions. 



The older post-larval forms of the cod and its allies, as 

 already described, seek in the various bays the margin of the 

 rocks in search of the abundant food there ; but it is not proved 

 that there is any general migration from deep to shallow 



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