38 EARLY STAGES OF TEREBRATULINA. 



that Leuckart has for a long time placed the Polyzoa with the Vermes, and in a new 

 edition of the " Outlines of Comparative Anatomy," * Prof. Carl Gegenbaur removes the 

 Polyzoa from the Mollusca, and associates them with the Vermes. 



EXPLANATION OF PLATES. 



PLATE I. 



Fig. 1. A few eggs in their natural position, from pallial membrane of an adult individual. 



Fig. 2. Earliest stage noticed. This was attached to rock, resting upon broad hinge margin. 



Fig. 3. Another stage in which the body has rapidly lengthened, and the peduncle is equal in length to 

 the remaining portion of the animal. 



Fig. 4. Stage in which a few cirri are developed with the oesophagus and stomach hanging below. 



Figs. 5, 6, 7. CEsophagus and stomach of last individual, showing different conditions of expansion and 

 contraction of the parts. 



Figs. 8, 9. Partial lateral views of the shell of fig. 3. 



Fig. 10. Represents the animal at rest, and in action. 



Fig. 11. The same from above; the arrows indicating the direction of rotation. 



Fig. 12. A state more advanced, with the liver as a simple hepatic fold on each side of the stomach. 



Figs. 13, 14. Different states of contraction of incipient hepatic folds of fig. 12 ; and showing cardiac 

 contraction in fig. 14, c. 



Fig. 15. Crown of cirri to show calcareous spiculse. [For distinctness and to simplify the drawings, the 

 cilia clothing the cirri are only shown in fig. 4, the simple outline of cirri in fig. ]2 and the calcareous spiculae 

 in fig. 15. It will be understood, however, that each figure possesses all the characters of the others.] 



Fig. 16. Portions of two cirri highly magnified to show more plainly the form of spiculas. 



Fig. 17. Alcoholic specimen in which divaricator muscles were visible owing to contraction of the parts 

 in alcohol. This is the only figure drawn from a preserved specimen. All the others are from life. 



Fig. 18. A portion of haemal valve. 



Fig. 19. A portion of neural valve. 



Fig. 20. The same portions before separation. 



Fig. 21. A slightly more advanced stage, showing crown of cirri. 



Fig. 22. A still more advanced stage, with haemal valve forcibly thrown open, showing divaricator muscles 

 with stomach between. The crown of cirri shows first indications of its bilobud character. 



Fig. 23. An hepatic mass from one side ; at this stage showing the first forming of caecal folds. 



Fig. 24. A stage more advanced ; valves forcibly separated in which all the parts are plainly seen. 



Fig. 24, A. A highly magnified view of the stomach, hepatic folds, lateral bands, etc., of fig. 24. This 

 figure shows a faecal mass rolled in a spiral form, in the act of being discharged through the mouth. The line 

 bordering the upper portion of the figure indicates the inferior margin of the crural process. 



Fig. 25. The haemal valve with crown of cirri, etc. 



Fig. 26. A view of fig. 22 with the valves closed. 



PLATE II. 



Fig. 27. A stage considerably more advanced than preceding ones, showing lophophore already bilobed, 

 the cirri, however, not deflected. The caecal lobules of liver few in number but separated. In fig. 23, plate I, 

 the lobules are just indicated. 



Fig. 28. Showing lophophore, with cirri deflected. The stomach and blind intestine hanging below. 



Fig. 29. The arms of the lophophore more sharply bent; the central processes first indicated. The highly 

 flexible lip is here seen in folds. 



1 Grumkiige der Vergleichenden Anatomie. Zweite ungcarbeitete Auflage. Leipzig, 1870. 



