Abstract
Male and female specimens of Terrapene Carolina (L) were collected early in the breeding season and kept in pens. The times of egg-laying were observed, and the eggs were removed from the nest within a few hours after they were laid. Each clutch of eggs was planted separately and records kept of the time of laying. From these eggs 40 living embryos were procured, upon the basis of which this report is made.
It was found that the age of the embryo as calculated from the time of egg-laying could not be depended on as an index of the degree of development. Embryos of the same clutch in some cases differed considerably in this respect; and great difference appeared between clutches of the same age. Obviously eggs develop in the oviduct of this species for various periods. It was largely a matter of chance, therefore, in selecting eggs for study with reference to particular phases of development; although an embryoscope improvised upon a 6-volt, 108-watt, ribbon filament Mazda lamp was of considerable assistance in approximating the age desired.
Spontaneous movements occur, apparently for at least several hours, before movement can be elicited in response to touch. Embryos with carapace-length of 6 mm. respond to touch on the snout, but not to touch on other parts, except possibly on the shoulder on very rare occasions (probably spontaneous movement in these instances). The movements at this time always involve the head and neck, and usually, also, the trunk, tail, and fore and hind limbs. The limbs never move in this phase of development without movement of the trunk. These reactions are total reactions, inasmuch as a more caudal or distal part does not move without movement of the more anterior or proximal part.
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