ILLUSTRATIONS. 93 



PLATE XXIV. 



(All figures of Nolocrinus virilis.) 



FIG. 1. Fully formed larva, in ventral aspect. X28. 



Fid. 2. Larva, mounted in balsam so as to show the skeleton. In the posterior end are seen the glandular 

 sacs. One supplementary plate is seen besides the primary terminal stem-plate. Dorsal 

 view. X55. 



Fia. 3. Side view of a larva with a process apparently coalesced with the marsupial wall. Four supple- 

 mentary terminal plates are seen. The glandular sacs were not distinct in this specimen. X 55. 

 FIGS. 4, 5, 6. From a series of sagittal, longitudinal sections of the larva. 



Figure 4. A nearly median section, showing the anterior prolongation of the parietal canal. 



Figure 5. A somewhat more lateral section in which is seen the hydrocoel. 



Figure 6. A still more lateral section, showing a downward prolongation from the parietal canal : 



the closed pore canal. 



The indentation in the anterior end of the two first of these figures is the suctorial disk. In figure 6 

 the anterior part has been slightly restored. There are thirty-five sections between figures 

 4 and 5, eighteen sections between figures 5 and 6. X80. 

 FIGS. 7, 8, 9. From a series of frontal, longitudinal sections of the larva. Figure 7 the more dorsal, figure 9 



the more ventral of the sections. 

 Figure 7 shows four glandular sacs in section. 



Figure 8 shows part of the anterior prolongation of the parietal canal. 



Figure 9 shows the hydroccel and the downward prolongation from the parietal canal representing 



the closed pore canal. The small accumulation of cells, marked ** in the anterior part is part 



of the anterior prolongation of the parietal canal. The little space between the two parts of 



the hydrocoel is part of the oral (left) ccelom and is seen to unite with it a few sections farther on. 



There are 28 sections between figures 7 and 8, 10 sections between figures 8 and 9. X80. 



PLATE XXV. 



(All figures of Notocrinus virilis.) 



FIGS. 1, 2, 3, 4, 5, 6. From a series of transverse sections of a larva, figure 1 being the anterior of them. 

 (A continuation of the series is given in plates xxvi, figures 1 to 3.) X70. 



Figures 1 and 2 are from the part above the vestibulary invagination, through the region of the 

 suctorial disk, which is indicated by the double indentation. In the middle is seen, below the 

 thick ectoderm, the nervous system, undivided, almost ganglion-like in figure 1, branching 

 in figure 2. A little inside the nervous system is seen the section of the narrow anterior pro- 

 longation of the parietal canal, and nearer the middle is seen the chambered organ. 



Figure 3 is from the anterior part of the vestibulary invagination; the nerves have dis- 

 appeared, but in the interior are seen, as in the foregoing sections, the parietal canal and the 

 chambered organ. 



Figure 4 shows the origin of the pore canal from the parietal canal. The small space seen between 

 this and the dorsal coelom is an anterior prolongation from the oral ccelom. The dorsal ccelom 

 is divided in the middle by the vertical mesentery. 



Figure 5 is from the region of the hydroccel. On the left side of the hydroccel is seen the anterior 

 prolongation of the oral ccelom; the space on the right side of the hydroccel is the parietal canal; 

 the dorsal ccelorn is an undivided space covering the whole dorsal side. In the skin to the left 

 of the hydroccel are seen two small spaces, the minor of them being the pore canal, the larger 

 a glandular sac. 



In figure 6 the oral ccelom has also appeared to the right of the hydroccel. 



There are two sections between figures 1 and 2, about sixty between figures 2 and 3, about thirty 



between figures 3 and 4, seven between figures 4 and 5, and sixteen between figures 5 and 6. 

 FIG. 7. Part of a section showing 3 glandular sacs. X290. 



FIG. 8. Part of a transverse section, in a slightly younger stage than that from which the series of transverse 

 sections have been figured, the vestibulary invagination being represented by only a slight 

 concavity. In the figure is seen an evagination from the oral ccelom, which appears to represent 

 a glandular sac in formation. The small ring seen outside the ccelom is the pore canal in section. 

 It is closed also in this specimen. X 105. 



PLATE XXVI. 



(All figures of Notocrinus virilis.) 



Fioe. 1, 2, 3. Continuation of the series of sections represented in figures 1 to 6, plate xxv. 



Figure 1 shows the beginning formation of the primary tentacles from the hydroccel: The oral 



ccelom is still divided in two lobes, one on each side of the hydroccel. 

 Figure 2 is from the region below the vestibulary invagination, also below the hydroccel. The 



oral ccelom now occupies the whole of the ventral side. Two glandular sacs are seen in either 



side of the larva. 



