of the Fishery Board for Scotland. 



247 



was a slight irregularity in the arrangement of the pigment spots, but it 

 generally was thus : — Two rows of dense black spots along each side, one 

 row close to the notochord when looked at from above, the other row 

 running along near the side of the fish. The spots composing each of 

 these rows were arranged two on each segment, so that each segment had 

 four black spots on each side — eight in all ; and they were so arranged on 

 the segments that the more dorsal spots were placed slightly in front of 

 the lateral ones. They thus formed a slightly lozenge-shaped figure when 

 viewed from the side, and were invariable in position. An irregular dark 

 and rather sparse spotting on the continuous median fin also occurred ante- 

 riorly. The irregularity in the pigmentation referred to was occasioned 

 by the somewhat varying position occupied by the yellow spots. As a 

 rule, these formed a kind of double row also on each side, and approxi- 

 mately in the same line as the black spots, but they were situated on the 

 lines of segmentation. There were thus two yellow spots on each side 

 (four in all) of each segment, or rather there were four half spots on each 

 segment. The following list gives various measurements of the young 

 wrasse made the day after hatching : — 



Tip of jaw to front of eye, 



. '10 



mm. 



?> 



back do., 



. '37 





)> 



front of ear, 



. -41 



ii 



>? 



centre of heart, 



. -47 



ii 



?) 



insertion of pectoral fins, . 



. -63 



ii 



j) 



anal aperture (apparently still closed), 



. 2-10 



ii 



JJ 



end of pigmentation, 



. 2-48 



ii 



JJ 



tip of tail (total length), . 



. 3-80 



ii 



Length of eye, ..... 



. -25 



ii 





ear, ..... 



. -23 



ii 



jj 



pectoral fin, 



. -41 



ii 



Breadth of head over eyes, 



. -52 



ii 



jj 



.,, ears, 



. -41 



ii 



jj 



(diameter) of heart, . 



. -06 



ii 



The nests are described above as being formed by the ballan wrasse. 

 When received, the Fishery officer was asked to describe or procure the 

 fish which constructed these nests, and on the 24th August he forwarded 

 two of the fish which form these nests, ' secured from the very ground 

 upon which the nests were found.' These were specimens of Labrus 

 maculatus, 235 mm. and 220 mm. long respectively ; and there seems no 

 reason to doubt the connection between these fish and the nests examined, 

 the more especially as it is recorded (Moreau) that both the L. maculatus 

 and L. mixtus construct nests for the reception of their ova. 



APPENDIX F. — No. VI. 



ON THE DEVELOPMENT OF THE COMMON MUSSEL (Mytilus 

 edulis, L.). By John Wilson, B.Sc, Demonstrator of Zoology, Uni- 

 versity of St Andrews. 



The common mussel is well known to all zoologists as the inhabitant of 

 tidal rock-surfaces and estiiarine flats. In the latter position mussels 

 attain to their fullest development, by reason of the abundance of food 

 available there, and the immunity from wave-action. The beds or scalps 

 may or may not be uncovered during ebb-tide. The largest specimens 

 live in the bed of the stream in whose estuary the scalps lie. In the bed 



