Xeniidae, [348]

Xenospongia patelliformis, [216]

Xiphacantha, [78], [78]

Xiphigorgia, [357]

Yaws, [121] n.

Yellow-cells (= Zooxanthella), [80], [86], [125], [261], [373], [396]

Yolk-granules of ovum of Sea-urchin, [7]

Young state of one pairing-nucleus essential, [34]

Yvesia, [224]

Zambezian Tick, infects man with Treponema, [121] n.