Stage 16 embryos have a greatest length of 8 to 11 mm and an estimated postfertilization age of 39 days.  The retinal pigment is distinct and the foot plate has formed.   The stage is represented by Carnegie embryo # 6517 that has a grade of excellent. It is considered to be the best specimen in the Carnegie collection at this stage. It has a greatest length of 10.5 mm (after fixation) and is considered to be in the most advanced third of the stage.

The embryo was prepared for microscopic examination around 1931. It was fixed in corrosive acetic acid, embedded in celloidin and paraffin and serially sectioned transverse to the long axis at 8 microns. The sections were mounted on 46 large glass slides and stained with alum cochineal (carmine). There are 1103 sections through the embryo.

The Browse part of the database includes 315 of the 1103 section images. Approximately every fourth section image was digitally restored and labeled, and can be viewed at four magnifications. Several 3D reconstructions were produced from the aligned section images. Animations of the 3D reconstructions of the embryo surface and flythrough animations of the aligned section images are included also on the disks. For anyone who wishes to use them for other reconstructions, research or presentations, all the original section images are available as individual .jpg files. The files are also available in archive files of the aligned low resolution images.

There are few published accounts of the specimen. Included on the disk are a few photographs of the embryo before it was sectioned. This specimen was included in the Atlas of Human Embryos (Gasser, R.F., Harper & Row, 1975). Also included on the disk are the figures from the atlas pertaining to embryo #6517.

Instructions for using the disks can be found by going to the Instructions section from the opening screen.