Periodicity of Growth and Change of Condition of Brook Trout (Salvelinus fontinalis) in Three Michigan Trout Streams

a reduction in the number of melanophores which were at one time present on the yolk-sac. This is explained by the expansion of the embryo and the reduction in the size of the yolk-sac, melanophores being transferred from the yolk-sac onto the body of the embryo. There is no indication of the aggregation of yolk-sac melanophores about the vitelline vessels such as has been described in Fundulus heteroclitus.