Explanation Of Plate I.

Fig. 1. Ascidioclava parasitica, enlarged.

Fig. 2. Section of body-wall of hydranth. gl., gland-cell of endoderm.

Fig. 3. Section of body-wall of lower part of hydranth and upper part of hydrocaulus.

Fig. 4. Section of base of hydrocaulus and adjacent portion of coenosarc. end., endoderm; m., mesogloea; ect., ectoderm.

Fig. 5. Medusa buds.

Fig. 6. Section of tentacle and part of umbrella. m., mesogloea; nb., nematoblast; v., velum; ex.n., ex-umbral nerve ring; r.c., radial canal.