Sexual reproduction is wanting, or takes place by the coalescence of a spermatium and a more or less developed female cell. The spermatia are naked masses of protoplasm, devoid of cilia and chromatophores. The female cell (carpogonium) is enclosed by a cell-wall, and after fertilisation forms a number of spores, either with or without cell-walls (carpospores), which grow into new individuals. The Rhodophyceæ may be divided into two families: 1. BANGIOIDEÆ. 2. FLORIDEÆ. Family 1. =Bangioideæ.= The thallus consists of a branched or unbranched cell-filament, formed of a single row or of many rows of cells, or of an expansion, one or two layers of cells in thickness, but without conspicuous pores for the intercommunication of the cells. The growth of the thallus is chiefly intercalary. The star-like chromatophores contain chlorophyll and are coloured blue-green with phycocyan, or reddish with phycoerythrin; all these colouring matters are occasionally found in the same cell (_Bangia_-species). Asexual reproduction by tetraspores, without cilia, but capable of amœboid movements. Sexual reproduction is wanting, or takes place by the coalescence of a spermatium with a carpogonium, which is only slightly differentiated from the vegetative cells, and is devoid of a trichogyne. The carpospores are destitute of cell-wall and arise directly by the division of the fertilised oosphere. The Bangioideæ occur chiefly in salt water. Order 1. =Goniotrichaceæ.=--The thallus consists of a branched cell-filament without rhizoids. Tetraspores are formed directly from the entire contents of the mother-cell, without any preceding division. Fertilisation unknown. _Asterocystis_, _Goniotrichum_. The _Goniotrichaceæ_, through the blue-green _Asterocystis_, are allied to the Myxophyceæ, and through _Goniotrichum_ to the _Porphyraceæ_.