226 W. G. RIDEWOOD. 



appear when the bud has readied the stage of development 

 represented in n. The structure which in g is marked jio.l. 

 miglit at first glance be taken for the developing fourth 

 plume; it is the lateral part of tlie post-oral lamella. 



Figure J represents the collar region and its appendages 

 (the plumes and post-oral lamella) of a bud a little older than 

 that shown in figure h; the buccal shield has been dissected 

 off from the one sideband the " body ^' and stalk from the 

 other, Tlie position of the mouth is indicated in the figure, 

 but tliis region is always more or less damaged in making 

 such a dissection as that described. The torn stalk of the 

 buccal shield in this preparation — as also in the similar pre- 

 parations shown in text-fig, 3, n, o, and \i, and in other of 

 the text-figures — occupies a position intermediate between 

 the mouth and the bases of the first pair of plumes. In 

 figure J the fourth plumes are hemispherical projections at 

 the bases of the third plumes^ touching those on the one side, 

 and in continuity with the post-oral lamella on the other. 

 Traces of pinnules are appearing on the first and second 

 plume-axes, and the terminal end-bulbs of these same plumes 

 are swelling out. 



In K the fourth plumes are now longer than broad, and 

 the fifth pair are making their appearance, l is a side view 

 of a bud of about the same stage as k, as may be determined 

 by comparing the development of the fourth and fifth plumes 

 in the two buds. Pinnules are now appearing on the third 

 plumes, and it will be noticed, in the case of the first, second, 

 and third plumes, that the pinnules ai'e not laterally placed 

 on the plume-axes, but ventro-laterally, and the groove 

 between the two rows of pinnules of each of the plumes in 

 question opens ventrally, or vcntro-hiterally, towards the 

 dorsal or stalked side of the shield. 



The figures in text-fig. 3 continue the series shown in 

 text-fig. 2. M is a little more advanced than i, of text-fig. 2; 

 the fifth plume is now hemispherical in shape; pinnules are 

 appearing* on the fourth plumes, and the end-bulbs arc 

 becoming differentiated. The end-bulbs of the first, second, 



