62 BULLETIN OF THE 



the ganglion gradually assuming the position it has in the adult, on the 

 anal side of the pharynx at the base of the anal tentacles. 



A section across the pharynx in such a stage as Figure 83 is shown 

 in Figure 87. A comparison with Figure 51 (Plate V.) of my Crista- 

 tella paper (Davenport, '90) will show a great similarity of conditions at 

 about the same age, and can leave no doubt concerning the homology of 

 the regions marked in both cases lu. gm. ; or compare Taf. VIII. Fig. 100, 

 nh., of Braem's ('90) magnificent work. A section through a later stage 

 is shown in Figure 82. The brain has already sent out circumoesopha- 

 geal nerves, as in Paludicella. The central part of the ganglion does 

 not stain ; one sees only a granular mass, sometimes with signs of short 

 fibres. In the cornua (nf) one occasionally sees very large clear nuclei 

 with a single nucleolus, lying in the midst of a cell mass which is 

 spindle-shaped and stains more deeply than adjacent cells. These remind 

 one strongly of bipolar ganglionic cells, but fibres could not be traced 

 far from their pointed ends. Series of sections of Flustrella parallel to 

 Figure 82 show, as one passes below the level of the ganglion, a con- 

 tinuous band of cells extending down from it towards the cardiac valve 

 and between the cell layer lining the oesophagus and the surrounding 

 mesoderm. One is reminded of the exactly similar conditions in Palu- 

 dicella (page 26), and of the " linienartige Zeichnung" seen by Nitsche 

 ('71, p. 431) and Yigelius ('84, p. 42) in the same place in Flustra. 

 These facts go to indicate the existence of a gastric nerve. 



At about the time at which the ganglion arises, the cavities of the 

 stomach and the oesophagus become confluent (Fig. 86 oe.). At this 

 stage (somewhat earlier than Figure 86) the alimentary tract consists 

 of a U-shaped tube of nearly uniform calibre, and without any indica- 

 tion of the coecum. The tentacles lie in two parallel rows in the middle 

 of the bud, the corona being incomplete both in front and behind, but 

 less so oral wards than towards the anus (Fig. 77, atr.). In fact, while 

 new tentacles are formed later towards the oral median line, they never 

 appear behind the line atr. This hinder region has another fate. Its 

 wall increases very greatly in area, diminishes correspondingly in thick- 

 ness, and forms a lai'ge part of the karaptoderm lying behind the post- 

 oral tentacle in Figure 86. With this growth of the kamptoderm the 

 ani;s is carried backwards, and farther and farther from the posterior 

 ends of the rows of tentacles, immediately behind which it formerly lay. 



As the kamptoderm grows in area, the polypide comes to lie in the 

 proximal part of the zooecium. Pari passu with this process occurs the 

 rotation of the oral tentacles, as in Paludicella. The oral tentacles which 



