St. Andrews Marine Lahoratory. 57 



black, though a few yellow chromatophoves are present. The 

 eyes also have pigment-specks; the caudal shows embryonic 

 rays. The yolk has considerably diminished. The otocysts 

 are still elongated from before backward, but present a double 

 outline from the differentiation of the capsule. 



'J'he larv£B daily increased in activity and size, and the five 

 groups of chromatophores became very distinct, viz. one on 

 the body over the middle of the yolk, another at tiie rectum, 

 tv/o conspicuous bars behind the latter (often broken up into 

 a dorsal and a ventral band), and a small fifth near the tip of 

 the tail. In the more advanced and more active larva3, with 

 the yolk much diminished, the pigment is more continuous. 

 Those with a large amount of yolk swim with a wriggling 

 movement. By reflected light the colour of these larval forms 

 is greenish yellow, and thus it differs from the chrome-yellow 

 of the younger stage. This change of hue appears to be due 

 to the development of the black pigment amongst the yellow. 

 The increase in the size of the pectorals in a few days became 

 marked, and though usually carried more or less obliquely, 

 they were ian-shaped when viewed from above. 



The chief changes till the 20tli April were the deepening 

 of the marginal fin both dorsally and ventrally and the exten- 

 sion of the chromatopliores (both yellow and black) from the 

 line of the body into the marginal fin at the two conspicuous 

 bars behind the vent, and the appearance of stellate black 

 pigment-corpuscles along the ventral edge of the fin. Stellate 

 black corpuscles also occur on the abdomen, and the eyes are 

 bright silvery. The yellow pigment still forms a line over 

 the medulla and the first part of the cord. The caudal 

 pigment-bar is chiefly of black corpuscles, only two or three 

 yellow being present. The pectoral fins are larger and have 

 rays ; the upward slant of the mandible and the reduction of 

 the yolk to a small round ball complete the features at this 

 stage. 



3. On the Spavming-period of A^onns. cataphractus 

 and the Vitaltty of its Ova. 



Parnell gives May as the spawning-period of this species. 

 Couch says nothing more than that the spawning-period is 

 stated to be spring ; while Day describes a female, 5 inches 

 long, from Southend, in February, as having its compara- 

 tively large eggs nearly ripe. In the " Researches " * it was 

 stated that the females caught in the sprat-nets in tiie Tay 



* Op. cit. p. 674, 



