ILLUSTRATIONS. 87 



PLATE IX. 



(All figures of Tropiumrtra carinala.) 



Fia. 1. Embryo 21 liours old, with the first rudiments of the slceleton. X250. 



Fia. 2. Embryo 24 hours old; tlie skeleton slightly advanced beyond figure 1 ; tlie first rudiments of the infra- 

 basalia are seen. X250. 



Fia. 3. Embryo 30 hours old. The body of this larva not very well preserved, so the position of the vestibu- 

 lary invagination could not be seen. Only two infrabasalia are represented, the third probably 

 hidden by the basal phite. X250. 



Fia 4. Embrj'o 40 hours old, seen from the ventral side. X250. 



Fig. 5. Abnormal embryo G days old; the vestibulum incompletely closed. X300. 



Fio. 0. Abnormal cmbrj'o G days old, pipe-shaped. The vestibulum incompletely closed. X300. In 

 figures 5 and 6 the details of the calcareous plates not quite exact; on account of the dark 

 color of the object the details could not be drawn with the camera. 



Fia. 7. Embryo S d;iys old, the skeleton dissolved. X180. 



Fia. 8. Embryo of same age as the one represented in figure 7. Normally closed vestibulum, into which 

 the primary tentacles are seen to protrude. X 180. 



Fia. 9. Upper part of a young Pentacrinoid (5 days old), decalcified; in the ve.stibulum, which is about 

 to open, are seen the tentacles (only some few of them drawn). On the left side are seen the 

 pore canal {po. c.) and the stone canal (st. c). The axial organ (ax.) is seen passing from the 

 chambered organ {ch. o.) up between the stomach and rectum. X260. 



PLATE X. 



(All figures of Tropiomelra cannula.) 



Fia. 1 . Embryo 20 hours old. X 180. 



Fia. 2. Embryo 40 hours old; drawn from a specimen stained with paracarmin and cleared in Canada 



balsam. In this specimen the continuation of the second ciliated band along the inside of 



the edge of the vestibulum could not be seen, but it was fairly distinct in another specimen 



of the same age. X 180. 

 Fig. 3. Normal young Pentacrinoid 6 days old. The infrabasalia could not be discerned on account of the 



dark color of the embryo. The details of the plates for the same reason only partially quite 



correct. X 180. 

 Fia. 4. Young Pentacrinoid G days old. One of the infrabasalia is abnormally situated outside the calyx 



and therefore distinct. X200. 

 Fia. 5. Young Pentacrinoid 6 days old. X200. 



Fig. 6. Pentacrinoid, fully formed, with the vestibulum opened and tentacles protruding. X200. 

 Fia. 7. Pentacrinoid with the beginning formation of the anal plate. X70. 

 Fig. 8. The calyx of the same specimen as figure 5. The first sacculus is indicated. X180. 

 Fia. 9. Calyx of young Pentacrinoid, seen from above. X200. 

 Fia. 10. Lower stalk-joints and terminal stem-plate of Pentacrinoid from the surface fihn. X200. 



PLATE XL 



(All figures of Compsomdra serrata. All X 290.) 



Fig. 1. Sagittal section of a young embryo, showing the beginning formation of the vestibulary invagina- 

 tion and the suctorial disk. The right coelomic vesicle somewhat swollen at the anterior end. 



Fia. 2. From the same series as figure 1, separated from the latter by five sections; shows the arrangement 

 of both ca?lomic vesicles, entoderm and hydroca'l. 



Fig. 3. Longitudinal, oblique section, showing the formation of the parietal canal from the hydrocoel. The 

 ciliated bands have begun to form. 



Fia. 4. Sagittal section of an embrj'o slightly older than the specimen represented in figures 1 and 2. The 

 formation of the vestibulary invagination, suctorial disk, and ciliated bands somewhat farther 

 progressed. The swelling of the anterior end of the right ca-lomic vesicle very distinct (begin- 

 ning formation of chambered organ). 



Fio. 5, G, 7. From a series of transverse sections of an embryo somewhat older than those represented in 

 figures 1 to 4; the vestibulary invagination considerably deeper; the chambered organ has 

 been formed, the parietal canal has opened to the exterior through the pore can:d; the hydro- 

 ccel has begun to form the primary lobes; the right ca?lomic vesicle covers the whole doisal 

 side of the entoderm. In figure 5 are seen the nerves in the edges between the vestibulary 

 invagination and the ectoderm. 



Fig. 8. Sagittal section through an embryo of the same age; shows the well-developed suctorial disk, the 

 anteriorly prolonged parietal canal, and the chambered organ. The nervous system very 

 well developed; the ciliated bands fully formed. Tlic small spaces along the strands of the 

 chambered organ show the place of the young stalk-joints. 



