. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ESTIMATION OF MELANOPHORE CHANGES 281 by the two holes, one each in the upper and lower margins of the tail near its root. As soon as the fin is stretched on the spatula the fin and spatula together are dipped momentarily in water at 60° C. This kills the tissues of the fin at once and thus stops any possible change in its melanophores. Such a method, which is the one used by Wykes (1937) and by me, is much quicker and therefore much more reliable than that employed by Waring, namely, fixation in Bouin fluid which, though a
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ESTIMATION OF MELANOPHORE CHANGES 281 by the two holes, one each in the upper and lower margins of the tail near its root. As soon as the fin is stretched on the spatula the fin and spatula together are dipped momentarily in water at 60° C. This kills the tissues of the fin at once and thus stops any possible change in its melanophores. Such a method, which is the one used by Wykes (1937) and by me, is much quicker and therefore much more reliable than that employed by Waring, namely, fixation in Bouin fluid which, though a rapid killing agent, is by no means so rapid as heat. From the hot water the spatula and its attached fin are then transferred to a preservative such as formaldehyde-alcohol where they should remain about half a day. The pre- servative regularly used in this work was a mixture of equal parts of 95 per cent. FIGURE 3. Preparation of the tail-fin of the catfish Ameiurus with two caudal bands. The upper band is partly blanched but not as much so as the rest of the tail. The lower band was cut at the same time as the upper one and blanched at the same rate as that one did. Before the preparation was made the lower band was recut whereupon it darkened as compared with the upper band. Parker (1943). alcohol and 10 per cent aqueous formaldehyde. The success of the operation thus far depends upon rapidity. The period from the moment the fish is decapitated till its fin is histologically fixed by hot water must be as short as possible. With practice this interval can be reduced to some 25 seconds. So short a time is of no significance for the pigment movements in many fishes where, as in the catfish, the pigment change is a matter of hours or even days. The technique here de- scribed would of course be useless for a species such as the squirrel-fish whose change of pigment may be completed in as short a time as five seconds. In fishes the rate of whose color change is moderately slow,
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
