38 EARLY STAGES OF TEREBRATULINA, 



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

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

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



ExPLAifATiox 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 attaclied to rock, resting upon broad hinge margin. 

 Fig. 3. Anotlier 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. OEso])hagus 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. Diffc-reut 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 spiculaa. [For distinctness and to simj^lify the dra\\-ings, the 

 cilia clothing tlie cirri are only .shown in fig. 4, the simple outline of cirri in fig. 12 and the calcareous spiculaj 

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

 Portions of two cirri highly magnified to show more plainly the form of spicuke. 

 Alcoholic specimen in whicli divaricator muscles were visible owing to contraction of the parts 

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

 A portion of h^mal valve. 

 A portion of neural valve. 

 The same portions before separation. 

 A slightly more advanced stage, showing crown of cirri. 



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

 witli stomach between. The crown of cirri shows first indications of its bilobed character. 



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

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

 Fig. 24, A. A higlily magnified view of the stomach, hep.atic folds, lateral bands, etc., of fig. 24. This 

 figure shows a faecal mass rolled in a sjiiral 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 cin-i, 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 imlicntod. 



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. 



^ Grundzlige dor Vergleichenden Anatomie. Zweite ungearbeitete Auflage. Leipzig, 1870. 



