jS2 PAPERS FROM TORTUGAS LABORATORY vol. xxxiv 



variable in number than in Pomacentrus adustus, as in a total of 72 the number 

 varied from 17 to 21. The arrangement of scales on the preopercle provides the 

 most distinctive specific criterion (aside from color markings), the scales of the 

 lowest row being very greatly reduced, or wholly lacking, leaving a broad border 

 below and behind almost free of them, the three rows remaining with 4 or 5 

 scales each, or a scale or two less to the row than in P. xanthurus. 



The young, down to 25 mm. or less in length, are abundant in early June. 

 From much blue spotting they are bright blue anterodorsally and shade grad- 

 ually to yellow posteriorly and ventrally. An imaginary line from the base of 

 the 4th dorsal ray, tangent to the eye below, approximately separates the two 

 color regions. A pair of blue lines runs from the tip of the snout toward the upper 

 orbital margin. On the soft dorsal, high above its base and just behind the last 

 spine, is a dark blue spot ocellated with lighter blue. As the fish grows, this 

 gradually becomes diffuse and is at last lost in the dark ground color. Neither 

 adult nor young has at any time a dark spot on the dorsal side of the caudal 

 peduncle. 



Adult males are larger than females and differ from them in coloration, com- 

 monly being bluish black, with more or less evident brassy spots on the scales of 

 the lateral line and those above it. The females are browner, with the lobes of 

 the dorsal and anal and the entire caudal yellow, inclining toward orange. The 

 blue spotting in both sexes may be relatively inconspicuous in mature fish, but 

 preservation in alcohol brings it to view again, whereas formalin is likely to 

 leave it obscure. At night the sexes become alike in appearance, both becoming 

 uniform gray above. The light color extends from the eye posterodorsally to mid- 

 level on the side, straight back, and then upward just behind the soft dorsal; 

 anterior margins of pectoral, anal, and soft dorsal blue; a blue sheen on the soft 

 dorsal, anal, and caudal. 



The female deposits her eggs in places of divers sorts, such as empty Strom bus 

 shells, dead Pinna shells still standing with gaping valves, and natural or ex- 

 cavated shelters beneath corals living or dead; they were found also in empty 

 tins and under masses of rusting iron. 



Females may begin breeding at a length of 55 mm. The ovarian eggs vary 

 much in size, which is consistent with a breeding season extending from June 

 to August and probably much longer. The eggs are about 1.2 mm. long and 0.5 

 to 0.6 mm. in greatest diameter, circular in cross section, and bluntly rounded at 

 the ends. They stand close together in a single layer and are attached to the sub- 

 stratum by a tuft of filaments at the animal pole. To the naked eye, in early 

 stages of development they appear bright yellow. Microscopic examination shows 

 that the color at first is localized in the blastodisk, later pervading all the devel- 

 oping germ. The yolk is coarsely granular and colorless. Embedded in it toward 

 the outer pole is a spherical opaque mass, 0.3 mm. in diameter, to the surface of 

 which oil droplets adhere. The same female, or perhaps different ones, may lay 

 in the same shell or other shelter at short intervals, for contiguous patches of eggs 

 in as many as four stages of development have been observed. 



The deposition of eggs is preceded by a display of mating reactions, glimpses 



