61. 



observed. Neither do tlie cerebro-pedal commissures seesn to }iavc 

 a double origin. 



7, The otocysts are not connected with the surface by 

 canals. Canals, apparently in process of degeneration, figii^res 

 21 and 22, ot, are present in adults. 



8« Both an anterior and a posterior aorta -irs- present. 



EMBRYOLOGY. 



1. The original surface cells seem to gi^re rise to the 

 test, the cerebral ganglia, the apical plate, and a new ectoderm, 

 inside the test. 



2. The cerebral ganglia, figures 46 and 47, are formed as 

 invaginations from the surface. 



3. The otocysts contain otoliths before the test is cast. 



4. The test, the apical plate, the stalk connecting the 

 test with the anterior portion of the body, and the stomodaeuia^to 

 the position of the definitive mouth, are all cast away. 



5. It seems that tii» t3rpical molluscan larvae maj'' have 

 been developed from embryos resembling those of Yoidia. 



LITERATURE CITED. 

 1. Brooks : On an Organ of Special Sense in the 



