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REPORT ON ZOOLOGY, MDCCCXLIV.

Annelids is simplified to an extraordinary degree. In theTubicolse the blood circulates partly in vessels, partly inlacunae; in Doyeria, Quatref. (allied to Syllis) there is onlya simple dorsal vessel, and in Aplilebine, Quatref. (allied toTerebella) neither branchiae nor blood-vessels exist. Withrespect to the sexual organs, Quatrefages (Comptes rendus,1844, p. 193; or Froriep’s n. Not. Nr. 674, p. 215) observeddistinct sexes in many Dorsibranchiata and Capitibranchiata.He (ib. 1844, p. 77 ; or Ann. d. Sc. Nat. t. i, 1844, p. 22)discovered on the coast of Brittany a Syllis, which, like theNereis prolifer a, Mull., was multiplied by spontaneousfission, after the development of a head upon the anteriorextremity of the portion of the body behind a posteriorconstriction. After the separation the two new individualsare exactly alike, but possess different properties. The an-terior individual probably reproduces its caudal extremity,whilst the posterior propagates itself by means of sexualorgans which are developed in it. The small species ofSyllis, Nereis, and Polynoe, which Quatrefages noticed to heluminous, are not, according to his researches (Annales d.Sc. Nat. t. xix, 1843, p. 184; or Froriep’s n. Not. Nr. 586,1843, p. 209), provided with any special luminous organs, asthe muscles alone develop the light during their contractions.Other researches have convinced him (Comptes rendus, t.xvii, 1843, p. 962; or Institut. 1843, p. 274) that freshwater acts like a poison upon the marine Annelids , which ischiefly owing to the want of chloride of sodium.

We are indebted to Oersted for a series of systematicessays on the branchiate Annelids . He proposes, instead ofthe older classification of them according to Audouin andMilne Edwards , and consequently instead of the divisionsinto Dorsibranchiata, Capitibranchiata and Abranchiata, thefollowing new classification. (Archiv , 1844, Bd. i, p. 99.)He divides them, according to their habitation, into Maricolse,Tubicoke, and Terricolte. But this arrangement cannotsuffice, since among the Maricolse there are also the bran-chiate Annelids which inhabit tubes, and moreover becausemany Terricolie live in water. In the classification of the