THE REARING OP SEA-FISH LARV^, 87 



the day. When the tow-nettiugs arrived, the bottles were always 

 allowed to stand for a few minutes in a convenient position near the 

 jars, so that the Copepods might concentrate themselves near the source 

 of light. They were then poured directly into the jars, or siphoned in, 

 according to the degree of their concentration. Thus the fishes were 

 surrounded by a superabundance of food during a portion of the day, 

 and as their instincts were obviously to catch a Copepod whenever the 

 chance presented itself, it is scarcely surprising that they should have 

 occasionally suffered from an excessive diet. For rearing work on 

 a larger scale I therefore believe that one of the many principles that 

 will need attention will be to avoid the possibility of the larvas enjoying 

 these periodic surfeits by securing a more uniform supply of food for 

 the fry than was attempted in these preliminary experiments. 



On October 1st, when the larvae in H were forty-five days old, my 

 diary states that the fry were all healthy and that they were already 

 giving up their pelagic habits so as to rest for considerable intervals on 

 the bottom of the jar, from which they would rise, however, from time 

 to time in search of food or from mere love of movement. 



On this day, as already related, I transferred the three survivors from 

 experiments I) and F to the same jar, in which they lived together 

 without loss for another period of five weeks, i.e. to the end of the first 

 week in November, although the smallest was removed on the 1st of 

 this month for preservation and anatomical examination. 



It measured 15 mm. in length, and the length of the pectoral fin was 

 4-9 mm. The dorsal fin possessed twenty-six rays (12 + 14) ; the anal, 

 eighteen ; and the caudal eighteen rays. The mandible, which pro- 

 truded in front of the upper jaw, possessed four teeth on each side of 

 a median gap. Teeth were also present in the upper jaw, but were not 

 counted. The supraorbital tentacles were invisible to the naked eye, 

 but could be detected with a lens as a pair of short unpigmented 

 papillae situated vertically above the most anterior margin of the pupil 

 of the eye. The eyes were set far forward, their anterior margins coin- 

 ciding with the frontal margin of the head. The pupil alone was blue 

 or black, the iris being golden. The black chromatophores on the head 

 formed a continuous sheet and were not arranged in radii. The colour 

 of the body (both living and preserved in formalin) was dark brown, 

 almost black, over the whole head region (top and sides), over the 

 anterior half of the abdomen, and over the pectoral and pelvic fins. The 

 entire caudal region was colourless and transparent excepting a single 

 line of chromatophores along the base of the anal fin. A line of 

 internal pigment ran along the spinal column as far back as the fifth 

 ray of the posterior dorsal fin. 



The other Bleunies, five in number, appeared to vary at this time 



