. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 184 JOAN C. RATTENBURY is difficult to remove the latter intact. The general appearance of the animal out of its tube is shown in Figure 1. Both mouth and anus open at the base of the coiled lophophore which bears the tentacles. The anus is borne on a papilla which is situated between the two arms of the lophophore, and the paired nephridia open on either side of this papilla near its base (Fig. 3). Below the lophophore there is a fold in the body wall forming the col- lar, and below this again is the tubular body which cont
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 184 JOAN C. RATTENBURY is difficult to remove the latter intact. The general appearance of the animal out of its tube is shown in Figure 1. Both mouth and anus open at the base of the coiled lophophore which bears the tentacles. The anus is borne on a papilla which is situated between the two arms of the lophophore, and the paired nephridia open on either side of this papilla near its base (Fig. 3). Below the lophophore there is a fold in the body wall forming the col- lar, and below this again is the tubular body which contains the digestive tract, the longitudinal blood vessels and the gonad. There are four longitudinal mesenteries which divide this part of the body cavity into four coelomic spaces. As can be seen from Figure 2 these mesenteries are not evenly spaced along the circumference of the body and consequently the left and right posterior chambers are considerably smaller than are the two anterior chambers. The afferent blood vessel lies within the right posterior chamber and the efferent vessel within the left anterior chamber. FIGURE 3. The oral end of the animal, posterior view, ap—anal papilla, c—collar. (Fig. 2). In the reproductive region of the body the efferent vessel gives rise to many short, blind branches, or capillary caeca (Fig. 2), and it is around these vessels that the gonads develop. The reproductive tissue is found only in the two anterior coelomic chambers, these areas being served by capillary caeca from the efferent vessel. The gonad is found in the aboral end of the body and may occupy from one- to two-thirds of the total length of the animal (Fig. 1 ). The body wall in this region is very thin and in season may become distended with gametes. The sexes are separate and may be easily distinguished during the breeding season, as the male gonad appears white and the female pink. At times other than the breeding season a tissue known as the fat-body ("Fett- ko
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
