ECHINODERMA. 9 



PLATE I. 



Fio. 1. Aurintlaria antardica viewed from the ventral aspect. Magnification 25 diameters, coe., the 

 spherical coelomic vesicle. 



Fin. 2. Some of the calcareous wheels of A. antardica. Magnification 200 diameters. ., seen from the 

 convex side, b., c., and cL, from the concave side. 



FIG. 3. One of the youngest of the Holothurioids in the collection, viewed from the side. Magnification 

 CO diameters. 



FIG. 4. A young Cucumarian, presumably C. lactea, dredged at Plymouth in 1905. Magnification 

 110 diameters. A key is given to this plate. 



PLATE II. 



FIG. 5. A median longitudinal section through one of the youngest Holothurioids in the collection. 



Magnification about GO diameters. The intestine is seen to be perfectly straight and very short, and 



the stone canal (st. c.) opens into a closed vesicle (ax.). 





 FIG. 6. A somewhat lateral longitudinal section through an older specimen than that represented in 



Fig. 5. Magnification 75 diameters. The axial sinus is seen to communicate with the coeloni by 

 a canal (mad.). 



FIG. 7. A median longitudinal section through a specimen about the same age as that represented in 

 Fig. 0. Magnification 75 diameters, pul., a diverticulum of the thin-walled rectum, which is in all 

 probability the rudiment of the pulmonary trees. 



FIG. 8, a., b., and c. Three transverse sections through one of the younger specimens. Magnification 

 75 diameters. 8. is through the tentacles ; Sb. through the middle region of the body, and 

 8c. through the posterior end ; g. ? curiously deeply-staining packets of cells resembling rudimentary 

 gonads. 



The restriction of the tube-feet to the three ventral interradii is seen, as also the fact that 

 the most terminal tube-feet belong to the mid-ventral radius. 



VOL. VI. 



