* Much of the information on which this section is based was obtained from Dr. M. Jean Allen, to whom we are most grateful.

These are large worms (often 30 cm. Iong and 10 mm. wide), which live in dark grey parchment-like tubes embedded in hard-packed sand. The tubes are often encrusted with shells, algal particles and debris, and have a lateral vent (Hartman, 1945). Intact animals are not often obtained, since they tend to withdraw into their long tubes when disturbed. The animals are yellowish to dark brown in color, and the sexes are separate. Sexually mature males: are white to yellowish in color; mature females are grey-green It is very difficult to distinguish between the sexes (Allen, personal communication).

Sumner et al. (1911) state that Diopatra is "almost ubiquitous" in Woods Hole waters. North Falmouth and Hadley Harbor, Mass., are among the collecting grounds for this form.

Bumpus (1898) reported that at Woods Hole the ova were "nearly ripe" in August; young larvae were obtained in tows at Beaufort, N. C. in July (Andrews, 1891a). Hartman (1945) found egg-strings exposed at low tide during June and July at Beaufort; she suggested that these egg-strings were probably deposited at night.

Allen (personal communication) has been successful in rearing embryos from the middle of June until the end of August, at Woods Hole. However, she has not found naturally-spawned egg-strings of Diopatra at Woods Hole any time during the period from April to the end of August.

A. Care of Adults: The animals do well, if they are left in their tubes and supplied with adequate amounts of running sea water. They are carnivorous and thrive if fed pieces of Mytilus every day or two (Allen, personal communication).

B. Procuring Embryos and Gametes: The naturally-fertilized eggs are surrounded by a gelatinous substance, and are deposited on the sand in long, slender, cylindrical egg-masses (Hartman, 1945). Various stages of embryonic development are contained within the jelly; when a freshly-laid string is placed in a culture tank, the larvae leave the jelly and seek the upper, light side of the container (Hartman, 1945). Ordinarily, however, they remain within the jelly-mass for a period of several days.

In the female, the ripe eggs are packed into the body cavity (Andrews, 1891b), apparently unattached to the ovary. The sperm are likewise found in masses in the body cavity of the male. Allen (personal communication) states that when the adults are held with forceps, they readily pinch off posterior segments. Eggs may be obtained from such isolated posterior sections by slitting the body wall; sperm ooze out when the body wall at the base of a parapodium is pricked with a dissecting needle.

C. Preparation of Cultures: Andrews (1891b) was not successful in obtaining development of artificially-inseminated Diopatra eggs. However, Allen (1951, 1953) reported that eggs could be successfully inseminated in vitro; the percentage of fertilization under such conditions is often not very high (Allen, personal communication). Just (1922) stated briefly (p. 477) that he was successful in artificially inseminating Diopatra eggs cut from the females.

After they are obtained, the eggs should be washed in a fingerbowl containing sand-filtered sea water. Inseminate with several drops of milky sperm suspension (in sand-filtered sea water); polyspermy should be avoided. It is: probably best to provide two or three changes of fresh, sand-filtered sea water within a few minutes after insemination, and at least once daily thereafter.

Normal DEVELOPMENT

A. The Unfertilized Ovum: The eggs of this form are produced in the ovary by a remarkable process which was described by Andrews (1891b). The ovarian tissue is composed of cell-strands which are thrown into loops, projecting into the body cavity of the female. One of the cells at the apex of each loop becomes enlarged and specialized, and gives rise to the ovum. The remaining cells (often 15 in number) of the loop continue to be attached to the ovum ( even after it is detached from the ovary and lies free in the body cavity) in the form of two long strands. These strands are retained until the ovum is almost ripe; however, Andrews suggests that the function of the "sister cells" is supportive rather than nutritive. Their subsequent fate, after detachment from the ovum, is not known.

The ripe egg, free of the two strands, is ovoid in shape; it is approximately 235 microns high and 205 microns wide (Allen, 1951). A considerable amount of yolk is present, rendering it heavy and opaque in the living condition. There is a striking aggregation of green pigment, in an area which is near the large nucleus (see Figure 4, Plate I, of the ripe egg of D. magna, in the paper by Andrews, 1891b).

B. Fertilization and Cleavage: Fertilization is external and takes place at the germinal vesicle stage (Allen, 1953). Two polar bodies are given off, and the first cleavage results in the formation of two unequal blastomeres. Subsequent divisions are of the spiral type (Allen, 1953), the four micromeres of the eight-cell stage being polar in position and somewhat smaller than the macromeres. Within three hours after insemination, functional cilia penetrate the egg membrane; anterior vacuolated cells form four plates, which surround a central mass (the source of the future apical tuft of the larva, according to Allen, 1953). Gastrulation is probably by epiboly.

C. Time Table of Development: The cleavage of Diopatra proceeds very rapidly (Allen, 1951). The following schedule is based on her data, at temperatures of 22-24û C.; the times are recorded from insemination and represent approximations, only, inasmuch as egg-batches vary considerably.

Stage First (and sometimes the second) polar body Two- to four-cells Eight-cells Mid- to late cleavage Functional cilia Apical tuft Rotating trochophores Elongated larvae

Time 30 minutes 40 60 minutes 60-90 minutes 90-120 minutes 3 hours 12 hours 24 hours 2-1/2 days

D. Later Stages of Development: The young larvae are spherical in shape, and provided with equatorial and terminal cilia, according to Andrews (1891b), which enable them to rotate within the jelly-mass. The egg membrane is apparently retained as a "cuticle" in the larva (Andrews, 1891b), and irregular patches of green pigment (presumably derived from the pigment of the egg) are scattered over the body.

Allen (1951, 1953, and personal communication) described the later stages of development in artificially-inseminated eggs as follows: An apical tuft forms within about eleven or twelve hours after insemination, and during the next 24 hours, elongated trochophores develop, which have a broad prototroch, a narrow telotroch, and red eyespots. These larvae continue to elongate, and by 60 hours have developed two or three sets of setae and a Y-shaped gut. Swimming is by a rotating movement. Allen (1951) reported that she was able to grow larvae in culture for as long as 21 days, by which time six sets of setae, pharyngeal muscle fibers, cerebral ganglion, tentacles, jaws and anal cirri were among the structures present.

SPECIAL COMMENTS:

Andrews (1891a) and Hartman (1951) comment on the fact that regeneration of the anterior end of Diopatra is a common phenomenon, and one which would be worthy of further study.

ALLEN, M. J., 1951. Observations on living developmental stages of the polychaete, Diopatra cuprea (Bosc). Anat. Rec., 111: 134.

ALLEN, M. J., 1953. Development of the polychaete, Diopatra cuprea (Bosc). Anat. Rec., 117: 572-573.

ANDREWS, E. A., 1891a. Report upon the Annelida Polychaeta of Beaufort, North Carolina. Proc. U. 5. Nat. Mus., 14: 277-302.

ANDREWS, E. A., 1891b. Reproductive organs of Diopatra. J. Morph., 5: 113-124.

BUMPUS, H. C., 1898. The breeding of animals at Woods Holl during the months of June, July and August. Science, 8: 850-858.

HARTMAN, O., 1945. The marine annelids of North Carolina. Duke Univ. Mar. Station, Bull. no. 2.

HARTMAN, O., 1951. The littoral marine annelids of the Gulf of Mexico. Publ. Inst. Mar. Sci., Univ. of Texas 2: 1-124.

JUST, E. E., 1922. On rearing sexually mature Platynereis megalops from eggs. Amer. Nat., 56: 471-478.

MONRO, C. C. A., 1924. On the post-larval stage in Diopatra cuprea, Bosc, a Polychaetous Annelid of the family Eunicidae. Ann. Mag. Nat. Hist. ser. 9, 14: 193-199.

RENAUD, J. c., 1956. A report on some polychaetous annelids from the Miami-Bimini area. Amer. Mus. Novitates, No. 1812.

SUMNER, F. B., R. C. OSBURN AND L. J. COLE, 1911. A biological survey of the waters of Woods Hole and vicinity. Part 1. Bull. U. S. Burl Fisheries, 31. 1-544.

WILSON, E. B., 1882. Observations on the early developmental stages of some polychaetous Annelides. Stud. Biol. Lab., Johns Hopkins Univ., 2: 271-299.