. Natural history of the American lobster... Decapoda (Crustacea); Lobster fisheries. NATURAIv HISTORY OF AMERICAN LOBSTER. 267 In the fourth stage the great claws are not only symmetrical, but of the toothed type. According to Emmel (96) the transition to the asymmetrical condition begins in the sixth stage, but in the material studied as a basis for this account it was impossible to detect any morphological differences until the seventh or succeeding stage. There is doubtless some variation in this respect. It is true that at preceding periods the big claws may differ in size or slightly in form as a consequence of molting or regeneration, but without implying the differentiation in question. Again at the seventh stage these. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.. Herrick, Francis Hobart, 1858-1940. Washington, Govt. Print. Off.