132 ECHINODERMATA, 



Multitudes of Pedicellarite drop from the Echinus on vitiation of 

 the water, or on the animal's decay. When transferred to a suitable 

 situation, they have been in motion for above a fortnight. The head also 

 separates from the stalk, and remains in considerable action, while the 

 rest disappears. 



On the whole, and especially from the size of the Pedicellarise being 

 in some respect proportioned to that of the Echinus, I feel rather dis- 

 posed to hold them integral parts of the creature's organization than 

 separate and independent parasites. 



In representing the Echinus, authors have been commonly content 

 with shewing only the shell, and some have exhibited the entire animal 

 with the spines in the greatest disorder, which proves that the specimen 

 had been distempered or dead, for nothing can be more regular during a 

 healthy existence. I doubt whether the secondary spines, adverted to 

 in description, are anything but perhaps younger spines in progress, un- 

 less ordinary spines regenerating. 



PLATE XXXI. 



FIG. 1. Echinus sphcera (Egg urchin, Professor Forbes), in motion ; a, suckers. 



2. Dental apparatus. 



3. Single, tooth front. 



4. Interior of the tooth. 



5. Cutting bone of the single tooth. 



6. Inner surface of the shell of a specimen, with the upper part of the 



dental apparatus, a, a, a. 



7. Inner surface of the segment of a shell without the dental apparatus. 



shewing the staples to which it is secured, a, a, a. 



8. Portion of the exterior surface of a shell. 



9. Cone of roe. 



PLATE XXXII. 



FIG. 1. Echinus sphcera, young specimen, under surface. 



2. Specimen with a red stellate form on the upper surface. 



3. Entire shell of an adult specimen. 



4. Portion of the surface of a shell. 



5. Ova. 



6. 7, 8, 9, 10, 11. Pedicellariac, enlarged. 



