POLYDORA COMMENSALIS ANDREWS—LARVAL DEVELOPMENT AND OBSERVATIONS ON ADULTS

¹ Marine Research Laboratories, University of Connecticut, Noank, Connecticut 06344

1. Polydora commensalis larvae were found in the plankton from July to November, 1963, and fertilized eggs were found in the tubes of adults in July and August.

2. Fertilized eggs develop into 5-segment larvae within 5 to 7 days, at which stage they are liberated to the plankton.

3. Ciliation, setation, pigmentation and other taxonomically important features are described for larvae from the trochophore to 29-segment stage. Planktonic larvae of all stages possess a dorsal median row of black ramified chromatophores. Advanced larvae may exceed 2 mm. in length. The pigmentation and large size attained are the most outstanding characteristics of P. commensalis larvae.

4. Due to the similarity between larvae of P. commensalis and P. hermaphroditica, a comparison of the two is given.

5. The length of larval life of P. commensalis is estimated to be between one and one and a half months.

6. Data on distribution, habitat and reproduction are reported. It is suggested that this annelid is more widely distributed than reported, and that fertilization is accomplished by copulation.