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December 25, 1929.

[[underline]] MEMORANDUM FOR COLONEL SHELDON:
 [[/underline]]

To carry out the studies of the conditions on the Upper Mississippi River Wild Life & Fish Refuge in accordance with the various conferences held between members of your Division and this Division, and the Chief's memorandum to Doctor Bell, it is suggested that collections of muskrats be made at four different points in the Upper Mississippi River region, preferably by four different persons who can carry on the work in a systematic manner. Ten muskrats should be taken at each station every ten days during the period from January 1 to April 31, and it would be desirable to save a series of 30 skulls of males and females in equal numbers. The sexual organs of both males and females of the animals taken should also be preserved.

The skins should be taken off and stretched in the regular cased fur method but half flesh side out and half fur side  out in each lot, each skin labeled on tag stretched through eye hole with date, sex, and locality. The skulls should each be labeled with sex, date, and locality on tag. The brains and thickest meat can be removed so they will dry up and not spoil but care should be taken not to injure any of the bones. The brains can be removed with a wire loop through the back opening. The embryos of the females and testacles of the males should be wrapped in little squares of cheesecloth, with the tag bearing date and locality tied around the neck of the cloth with four corners brought together to form a little bag. The embryos of the females will be found in the two horns of the uterus lying in the back just above and in front of the bladder. The whole uterus including the ovaries should be removed and sent in the little cheesecloth bag. Latar as the embryos become larger they will be easily located and recognized and will require a larger bag to hold the whole set in the uterus. The testacles of the males can be removed and labled in the same way in cheesecloth bags. Both embryos and testacles should be preserved in formalin, one part to nine parts of clear water in glass jars and after six days taking out and packed in tight tin boxes and sent by mail to the Biological Survey.

Acting in Charge,
Division of Biological Investigations.

EPB/ars