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Show 46 DR. J. MURIE ON IRREGULARITY [Jan. 13, 4. The depth of the body and root of tail differ as regards augmentation, the former being as 8 to 1, the latter as 5*9 to 1. 5. Between the width and depth of the operculum, respectively 5*7 and 7 to 1, the horizontal to vertical increase is inversely to what obtains in the body. Availing one's self of these considerations, and comparing specimens I. and II. with III. (Table B ) , it will be seen, more especially in the older fish, IL, that the maxillary bone and distance from snout to eye are proportionally larger than in the Parr. The same may be said as regards growth of the operculum, more particularly its depth. The distance between the ventral and anal fins is also sensibly greater. Thus those parts which in the adult, ceteris paribus, show the greatest relative accretion are, curiously enough, in the Salmonoids reared in fresh water, the parts which have most increment. From this it follows that whilst a general arrest of development, retardation of growth, or whatsoever the term used, has occurred from the altered physical circumstances, still the proportional magnitude of the parts has kept pace with that of a normally developed adult Salmon favoured by visits to the sea. GrENERAL CONCLUSIONS. The main fact at issue-Can Salmo salar live for series of years in fresh water without access to the sea?-if not settled beyond cavil, has, I venture to think, in this and the preceding paper, been tolerably well substantiated. At least the evidence of many observers has been given ; so that it remains for those who discountenance the view to show the fallacy of the data, and prove on evidence as reliable that the contrary is the true state of the case. This does not interfere with the necessity of further experiments being tried. For my own part, I am quite willing to bow acknowledgment to whichever side the truth lies on-though, after an impartial consideration, I cannot escape or reason away the strong presumptive allegations positively confirming the opinion. To me they are reasonable, because based on what, in homely parlance, are deemed everyday occurrences. The principle in the life-history of the Salmon which seems at variance with its customary habits is in reality not so; what takes place as a general rule is here but temporarily departed from. In the physical constitution of animals, the limits assigned to the well-being of the individual are not so rigidly exact as a mathematical problem; hence, to judge rightly, we must know all, or be prepared to confute abnormal phases of existence. In the present instance the choice of credence lies between testimony harmonious with laws regulating the primary growth of Salmon, and suppositions framed on circumstances we have but an imperfect knowledge of, unless it be satisfactorily shown that the statements of such a truthful observer as Yarrell, or the instance recorded by Anderson, are fictitious or egregiously false. Those who deny that some Salmon, few or many, can permanently accommodate themselves to a freshwater residence for a comparativelv |