348 PROCEEDINGS OF THE ACADEMY OF [July, 



edge, while the gastral end reaches to the deepest portion of the 

 mantle chamber (fig. 36). In all of these details as to the formation 

 of the intestine there is striking similarity between Fidgur and Crepidula. 

 In Crepidula the gastral end of the intestine o{)ens into a lumen 

 between the yolk cells, which give rise to the stomach and liver. 

 In Fvlg.ur I have observed no such lun\en between the yolk cells, and 

 while I think it probable that these cells form the stomach and liver 

 in this animal, I have not traced their history far enough to speak with 

 certainty upon this point. In Fulgur as in Crepidida the secondary 

 macromeres lie at the inner end of the stomodteum (fig. 31), and they 

 prol^ably form that section of the alimentary canal immediately follow- 

 ing the stomodieum. 



8. THE FOOT. 



The development of the foot is practically the same in Fulgur as in 

 other prosobranchs. It appears as a thickening of that portion of the 

 blastoderm lying between the otoc3'Sts behind, the blastopore in front, 

 and the pedal ganglia on the sides (figs. 29 and 30). It is at first wide 

 in -transverse direction and narrow antero-posteriorly and it is bilobed, 

 the two lobes being separated on the side of the blastopore by a groove 

 in which the blastoderm remains thin (figs. 30 et seq.). The foot then 

 gradually rises above the general level of the blastoderm until it 

 becomes prominent, becoming about half as wide from side to side as 

 in earlier stages (figs. 33, 34); at the same time it takes into itself the 

 pedal ganglia and otocysts. 



At the posterior end of the groove between the two lobes an invagi- 

 nation is formed which becomes the pedal gland (P. G., figs. 33, 34). 

 A transverse furrow on the surface of the f(X)t then constricts off a 

 smaller anterior lobe, the propodium, from a larger posterior one, the 

 mesopodium and metapodium (figs. 35, 36). 



9. LARVAL AND DEFINITIVE KIDNEYS. 



Rumiing laterally from the foot a ridge of cells develops on the right 

 and left sides; this ridge lies some distance posterior to the velum, 

 with which it is nearly parallel; its free border, or crest, becomes cre- 

 nated (figs. 34, 35, Ex.K.). This is the larval or external kidney and, 

 as in other prosobranchs, consists of large ectodermal cells which become 

 loaded with nitrogenous waste substances. It is an interesting fact 

 that the larval kidney of Fulgur does not appear until after the basis 

 of the i)ermanent kidney is present (figs. 32, 33), and its relatively 

 small size seems to indicate that it is never an important excretory 



