. The Cambridge natural history. Zoology. BRACHYURA—LARVAL HISTORY 183 the Glaucothoe of the Pagi^rids, resembles a small Galatliea or Porcellana, the abdomen being still large and unflexed and furnished with normal pleopods. From this stage the adult structure is soon achieved, though, owing to the continued growth of the Crustacea even after maturity is reached, there is often a slight progressive change in structure, especially in the male, at each successive moult of the individual. The Mega- lopa of Gorystes cassivelmmns is peculiar in the immense production of the second an- tennae, whic
. The Cambridge natural history. Zoology. BRACHYURA—LARVAL HISTORY 183 the Glaucothoe of the Pagi^rids, resembles a small Galatliea or Porcellana, the abdomen being still large and unflexed and furnished with normal pleopods. From this stage the adult structure is soon achieved, though, owing to the continued growth of the Crustacea even after maturity is reached, there is often a slight progressive change in structure, especially in the male, at each successive moult of the individual. The Mega- lopa of Gorystes cassivelmmns is peculiar in the immense production of the second an- tennae, which act as a re- spiratory tube (Fig. 125). The Brachyura must be considered under the follow- ing subdivisions:— Tribe 1. Dromiacea. All authorities are agreed that these ^ are the most primitive of the Brachyura. In them the abdomen is much. - -Ts •Sii^ir less reduced in both sexes F'°- 125.—Later stage (Megalopa) in the de- velopment of Corystes casdvelannus, x 10. A, Antenna ; Ab, 3rd abdominal segment ; C, great chela; 1'.8, last thoracic appendage. (After Gurney.) than in other Brachyura ; there is a common orbito- antennary fossa, into which eyes and antennae are withdrawn, instead of a separate one on each side for each organ ; the carapace is often much elongated as in the Macrura and Anomura, and a number of other anatomical characters might be mentioned which characterise the Dromiacea as intermediate between the true Brachyura and the lower forms. There are, however, two views as to the relationship of the Dromiacea; Glaus held that they proceeded from a Galatheid ' Bouvier, Bull. Soc. Philomath. Paris, (8) viii,, 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 Harmer, S. F. (Sidney Frederic), Sir, 1862- ed; Shipley, A. E. (Arthur Everett), Sir, 1861-1927. ed. [London, Macmillan and
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