62 The Irish Naturalist. [March, 



forms, by-and-by coalesce into a single large globule. The 

 larval fish carries tlie latter at the anterior part of the yolk- 

 sac just beneath the heart, and the cephalic flexure is marked, 

 though it may have been somewhat increased from premature 

 birth or abnormal surroundings. Dark-brown pigment- 

 corpuscles are scattered on the head and along the body to 

 the vent, some occur on the j'olk-sac, and a few at intervals 

 along the ventral edge oi the notochord to a more distinct 

 series in the caudal region. The dorsal (marginal) fin is 

 interrupted — at a point over a vertical cutting off the posterior 

 third of the yolk-sac — by a papilla which indicates the future 

 filament, the edge of the marginal fin dorsally and ventrally is 

 serrate, a feature not due to injury, but characteristic of this 

 form. The notochord appears to be unicolumnar in the 

 drawing, but further investigation is necessary on this point. 



The next stage, which is about 2*8 mm. in length, shows 

 considerable elongation of the bodj^, a shrinking of the yolk, 

 the carr>^ing of the oil-globule backwards, and a great in- 

 crease of the dark brownish pigment over the head, body 

 and yolk-sac as far as the vent. The dorsal filament projects 

 as a long papilla. The increase in the length of the latter 

 wdth its distal expansion, and the opening of the mouth are 

 the next changes. Then the process elongates still more, 

 presents secondary papillae and a long terminal flabellum with 

 dark pigment on the expanded part — composed of connective 

 tissue and skin. The eyes also show dark pigment. The 

 increase in the filamentous dorsal process and its appendages 

 is remarkable, the whole being little short of the length of the 

 fish and giving it a striking appearance. It w^as, indeed, 

 called by Gasco, Vexillifer De Filippi. Emery figures one 

 with ten processes on the filament in February. The basal part 

 of the filament becomes stiff, and from it the long, flexible, 

 tasselled distal region floats backward. The pectoral fin is 

 rounded. The peritoreal surface develops much dark pig- 

 ment. 



The function of the remarkable dorsal appendage is not 

 easily explained. It may be a sensory organ or a lure during 

 pelagic life, or may be a protective resemblance to certain 

 pelagic coelenterates. It by-and-by disappears by absorption 

 or otherwise, the adult form having been found by Prof. 

 Emery at 85 mm. A trace of the structure, perhaps, is seen 



