CIRCULATORY SYSTEM OF THE GIANT SCALLOP. 245 



blood from other portions is carried to the kidneys, from which 

 it is carried to the gills, and then back to the heart. A portion 

 may dodge the kidneys and go to the gills. Blood seems to act 

 both as blood and lymph. (See pp. 227-234 and Figs. 3, 4, 5 

 and 7.) 



Nervous System. The cerebral and pedal ganglia are small 

 and somewhat removed from their usual positions. The visceral 

 ganglia are very large and complicated in structure. The circum- 

 pallial nerves and the branchial nerves have ganglion cells 

 throughout their length. The otocystic nerves originate directly 

 from the cerebral ganglia. (See pp. 234239 and Figs. 6, 8, 

 9 and 10.) 



Phylogeny. Ontogeny and the probable conditions that have 

 resulted in the complication of structure, both seem to indicate 

 that the division of the Mollusca into lamellibranchs and gas- 

 tropods, took place at an early time, before the ancestors had 

 attained much complexity of structure. 



There seems to be no reason for believing that lamellibranchs 

 ever had more complicated head machinery than they have at 

 the present time. If this is true they probably have never had 

 need of more anterior ganglia than they now generally have. 

 (See pp. 239-243.) 



Anatomical Draivings. A combination of photographs and 

 drawings may sometimes save much time and tedious work. 

 (See pp. 243 and 244.) 



UNIVERSITY OF MAINE, 

 ORONO, MAINE, 



November 15, 1906. 



