The Journal of experimental zoology . ocessesthough the branchial character is more evident than specimen is from the same dish as the others (16 days afterfertilization). It is evident from these data that the rate of de-velopment of the diff^erent larvae in a single dish varies withinwide limits. At the stage represented in Fig. ice the inner sur-faces of the branchiae are covered with very active cilia. In order Biological Bulletin, 05, vol. viii. 2The tube secreted by the animal is at first a very short cylinder which is quite transparent and coversonly a small part of the larv
The Journal of experimental zoology . ocessesthough the branchial character is more evident than specimen is from the same dish as the others (16 days afterfertilization). It is evident from these data that the rate of de-velopment of the diff^erent larvae in a single dish varies withinwide limits. At the stage represented in Fig. ice the inner sur-faces of the branchiae are covered with very active cilia. In order Biological Bulletin, 05, vol. viii. 2The tube secreted by the animal is at first a very short cylinder which is quite transparent and coversonly a small part of the larva. The ring at first is situated near the anterior end of the body just backof the eyes. 42 Charles Zeleny. to get at the method in which these primary processes branch lateron, I have designated them arbitrarily by the Roman numerals I, IIand III. I represents the most dorsal pair, II the middle pair andIII the ventral pair, R or L being prefixed to represent right orleft when there is any need for distinction between the two Fig. dianthus. Larvae. Stages of transformation from free-swimming to sedentary views. A—Free-swimming larva. Age, 9 days. Shows long apical cilium (X208). B—Swimming but sluggish larva. Age, 9. days. Shows setae and shortened apical cilium (X185).C—^Attached larva (X90). Age, 17 days. Three pairs of head lobes. Beginning of secretion oftube. D—^Age, 17 days (X90). E—Age, 16 days (X85). F—Age, 17 days. Second of originalthree pairs of branchiae shows secondary branches ( X 70). Compensatory Regulation. 43
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