NOTES ON THE BIONOMICS OP MELLITA 1 



DR. W. J. CROZIER 

 University of Chicago 



Observations already recorded- led me to devote some atten- 

 tion to the movements and the coloration of Mellita sexies-per- 

 forata, and to the injuries which are in nature inflicted upon the 

 individuals of this species. The findings incidentally supple- 

 ment and confirm some deductions made in the notes cited, 2 

 and serve to indicate several directions in which further study 

 would seem promising. 



Mellita lives more or less completely buried in the sand, in 

 channels between islands, at the outlets of sounds, and between 

 the shore and the inner reefs ; but always in places where there 

 is a tidal current. The character of the bottom, which may lie 

 2 to 6 fathoms beneath low water, varies from shell-sand, gray- 

 white and usually muddy, to dark brownish mud. Young and 

 adults of all sizes up to 13 cm. transverse diameter occur in 

 company. The older individuals burrow more deeply than the 

 young ones, the latter frequently lying freely exposed on the 

 surface of the sand. In stormy weather, all the Mel I it as dig 

 themselves deep into the mud, to a depth of perhaps 8-9 cm. 

 In the laboratory the older individuals burrow more quickly 

 when exposed to bright sunlight than they do in the dark. He- 

 liotropism, when horizontal light is used, is not precise; younger 

 individuals tend, on the whole, to move away from a source of 

 horizontal light. Normally, light coming from above may be a 

 significant source of stimulation ; this was not adequately tested. 

 The low degree of photic irritability toward horizontal light 

 probably accounts for the fact that no photic orientation, strictly 

 speaking, was noted; such orientation might be expected, since 

 the nature of Mellita 's locomotion would make it possible. 



In locomotion on a solid surface, that part of the body ana- 

 tomically the anterior is always carried ahead. The "leading*' 



2 Crozier, W. J., 1918, "On the pignirntat ion <.f :i 1 'h pra-' r"i<l, .V- ' M 



435 



