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adjacent. On the riylit upper .side of the directive axi.s the tifth and sixth protocnemes, 

 incomplete from the beginning, have now disappeared, as is also the case with the pair of 

 metacnemes on the same side. Mesenterial filaments are no longer present on the dorsal directives 

 (IV, IV), and the pair of metacnemes has also disai)peared from the middle exoccele on the left 

 side, but the dorsal pair (A), though very feeble, still persists. 



The arrangement of the septal ingrowths, present as yet only on tlie left lower side, is very 

 instructive. The largest occur within tlie entocwle of the pairs of directives; two are found 

 between the left dorsal mesentery and the mesentery of the tirst bilateral pair (IV-II); two 

 between this last mesentery and the mesentery of the second bilateral pair (H-I), while only one 

 appears between this and the left ventral directive (I-III). Three of the septal invaginations 

 are exocoelic, the exocoele of the dorso-Iateral pair of protocnemes (II, V) is provided with one, 

 but the septum of the exoccele of the ventro-lateral pair (I, VI) is as yet undeveloped. The 

 entocoele of the persistent pair of metacnemes (A) also contains an invagination. 



In the section from a still lower region, represented in tig. 89, fully developed filaments 

 are retained only on the first three bilateral pairs of protocnemes. Only nine mesenteries are 

 present, the mesentery remaining in addition to the Edwardsian mesenteries is the fifth memlier 

 of the left side. A septum occupies each chamber between an}- two mesenteries, whether the 

 two constitute a pair or not; the septum in the entocoele of the left dorso-lateral pair is small, 

 and soon disappears along with mesentery V. The skeletal fragments within the middle of the 

 gastro-coelomic cavity' represent the first ai^pearance of the columellar projections. 



In fig. 90 only mere traces of six of the mesenteries persist, the first pair being the strongest; 

 the number of septa is also six, corresponding with the number of mesenteries. With one 

 exception the septa are all united in the middle, otherwise the gastro-coelomic cavity is divided 

 into as many separate chambers as there are septa. 



Another bud of about the same age presents a difl'erent condition with regard to the 

 appearance of the first two pairs of metacnemes from that just described (fig. 82). The 

 protocnemes are at the JE'dwardsia-stnge, and within each of the median lateral exocceles are the 

 rudiments of a bilateral pair of metacnemes (A, A), which are somewhat better developed in 

 sections below the stomodieum. 



The tentacles in the bud have already appeared, and exhi))it an interesting .stage. Fig. 83 

 is taken from a slightly o})li(iui> section, the upper half througli the free portion of the tentacles, 

 and the lower through their attachment to the periphery of the disk. The polyp was expanded 

 to such a degree that the peristome projected in a cone-like nuinn(>r ))eyond the zone of tentacles, 

 and, as seen in the middle of the section, the Edwardsian mesentaries extend as far as the 

 stomoda?al walls. Ten of the tentacles show a regular alternation of large and small members, 

 and, superposing the section on that in fig. 82, the tentacles arising from the entocoeles are seen 

 to be the larger, and those from the exocceles the smaller. In place of the single median lateral 

 prototentacle on each side are three tentacles, as yet incompletely formed. These will lie found 

 to correspond in position with the incipient pair of metacnemes in the median lateral exocceles, 

 and serve to establish that the metatentacles arise practically simultaneously with the metacnemes, 

 an entoco'lic and an exoccelic member together. 



A third bud. somewhat older than either of the two described, was also studied, and the 

 details of its lower region are represented on PI. XIII, fig. 91. The upper right side is the border 

 toward the centre of the colony, and the lower left side is the outer aspect. The relationships of 

 the mesentei'ies, as befoiT, show the inner border to be the sulcular aspect, and the outer border 

 the sulcar. In the stomodieal area six pairs of protocnemes and six pairs of metacnemes occur, 

 and of the foi'mer all the pairs are comjtlete on one side, but tlie members of the fifth and sixth 

 pairs are incomplete on the other side. 



In the region rei)resented only four pairs of the metacnemes occur, the two pairs on the 

 upper left side having disappeared some distance above. Mesenterial filaments occur on the 

 Edwardsian mesenteries, but not on the fifth and sixth bilateral pairs; and septal invaginations, 

 both entocnelic and exoccrlic, a))pear within practically all the mesenterial spaces. 



The lower sections demonstrate the same relation as in the jirevious bud, namely, that as the 



