1902.] NATURAL SCIENCES OF PHILADELPHIA. 779 



appearance. Each new tentacle arises not only just in front of a 

 sense-organ, but in a definite relation to the older tentacles. And 

 the same thing is true for the sense-organs. It is therefore possible, 



Fig. 14. 



from a study of successive stages, to predict where each new quar- 

 tette of tentacles or sense-organs will arise. The diagrams shown 



Fig. 15. 



in the text-figures are from camera drawings of mounted whole 

 raedusre. If we examine text-figure 14 we see that T. (tentacle) 



