468 Mr. J. H. Orton. Occurrence of Protandric [June 8, 



Sternberg. " Die Akromegalie," 1897. (New Sydenham Society's Translation, 1899.) 

 Tamburini. ' Centralbl. f. Nervenh.,' ] 894. 

 Vassale and Saechi. ' Eiv. sper. d. fren.,' 1892. 



Widal, Eoy, and Froin. 'Eev. de nied.,' 1906. (Case of Acromegaly without enlarge- 

 ment of pituitary, but with great increase of cyanophil cells and cysts.) 



Woods-Hutchinson. ' Trans. Pan-American Medical Congress,' 1894 ; ' New York 

 Medical Journal,' vol. 67, 1898, and vol. 72, 1900. 



On the Occurrence of Protandric Hermaphroditism in the Mollusc 



Crepidula fornicata. 



By J. H. Orton, A.E.C.S., Marshall Scholar in the Royal College of Science, 

 London (Imperial College of Science and Technology). 



(Communicated by Prof. Arthur Dendy, F.R.S. Eeceived June 8, — Read 



June 24, 1909.) 



Introduction. 



Crepidula fornicata is a streptoneurous Gastropod belonging to the 

 Calyptrseidse, a family of the Tamioglossa. It was first introduced into 

 England from America about 1880 (1), when it was imported with American 

 oysters. In America it is found on the east coast from Labrador to Florida, 

 but in England so far as is known, it is confined to the Essex and 

 Lincolnshire coasts, occurring, however, in abundance in shallow water in 

 the neighbourhood of the mouths of the Crouch and Blackwater rivers. The 

 conditions on the Essex coast seem to be highly favourable for its growth 

 and propagation ; indeed, so favourable, that within five or six years it has 

 over-run the oyster beds at West Mersea. By attaching themselves very 

 strongly to oyster-shells they cause the oyster fishermen much trouble, and 

 it may be remarked, by competing for food and oxygen with the oysters may 

 become a cause of much more serious trouble in the future. To obtain food 

 the animals raise the anterior part of their shell, and extending the head to 

 the front edge of the shell, move it slowly from side to side : at times the 

 whole shell may be similarly turned slowly round to the one side or the 

 other. 



Crepidula fornicata is sedentary for the greater part of its life. It forms 

 ■" chains," as Prof. Conklin calls them, by the curious habit the individuals 

 have of fixing themselves in linear series one on the top of another as in 

 fig. 1. Chains of as many as 12 individuals have been found. Viewed as a 



