440 Charles R. Stockard 



regenerates a wide mass of tissue. When undisturbed the narrow 

 end soon becomes bent around towards the new tissue forming at 

 the wide end and fuses with this in such a way as to finally adjust 

 the entire mass into a circular shape; the original portion of disk 

 border forms the periphery of the miniature disk (Fig. 4B). The 

 narrow end oftentimes folds too far and projects beyond the wide 

 portion. This imperfection is readjusted within a few days by a 

 process of puckering and subsequent flattening out of the tissue. 

 The newly formed tissue serves to unite the cut margins and 

 appears in the body of the small disk as only a limited amount. 

 The new tissue never continues to grow and cause folds or puckers 

 in the surface of the disk after the final assumption of the circular 

 form, but its growth is inhibited and stopped as it were by the 

 attainment of this shape. 



A V-shaped piece cut from the periphery towards the center of 

 the Cassiopea disk regenerates new tissue from the inner cut 

 angle and from its outer borders. The tops of the two arms are 

 parts of the original disk periphery containing sense organs which 

 cause the entire tissue of the V to pulsate (Fig. 5A). The nearest 

 possible approach to the disk-shape of the medusae that can be 

 attained by the V-pattern is a circular cup form. Such a form 

 is always assumed and its mode of development is somewhat as 

 follows. The newly regenerated tissues on the sides of the inner 

 angle of the V fuse, the apex then becomes bent owing to a tend- 

 ency to curl and the direction of this curl determines whether the 

 oral or aboral surface shall form the outer surface of the cup. 

 The new tissues from the outer edges of the V then fuse along their 

 borders as well as with the upturned apex. Thus the circular 

 cup is formed having the folded apex as a base, its wall of the old 

 V-arms and newly regenerated tissue and its peripheral border of 

 the old disk peripheral parts with sense organs and the edge of the 

 new tissue (Fig. 5B). The cup pulsates in a manner similar to a 

 medusae disk. Here again the regeneration of new tissue is 

 stopped when the walls are completely fused. Growth does not 

 continue and cause the cup wall to be thrown into folds, although 

 the prevention of the cup-shape would allow many times the amount 

 of new tissue present to be formed. 



