000 riiOCEEDlNGS OF THE ACADEMY OF [Aug., 



Sometimes tliey are withdrawn immediately, Ijut frequently an arm 

 crawls around for hours, or days, trailing tire cipcuui till it is withdrawn 

 or falls away. 



Probably if the caeca are not taken in within a few hoiu's the nuiscles 

 ose their elasticity and the caeca decay and drop off. Occasionally 

 these organs are left on the disk and sometimes the tube is broken in 

 such a manner as to leave them hanging like two coiled trails. After 

 freeing itself the ray crawls up the glass and stations itself with the 

 broken i)art downward and remains so for a long time. This is the 

 attitude of a single ray till all, or nearly all, the pyloric caecum assumes 

 its noi"mal position. 



After one arm is s(>)jarated, or even wlien it is going, another may 

 break away. 1 saw one animal try to break tlK> disk apart after having 

 lost two rays. It took many positions, strainc^d the (issues and worked 

 for hours, j)ut died before the disk was broken. 



Tlic results of my observations are: The breaking is automatic; and is 

 effected by pulling apart or fracture without strain; there is cijordina- 

 tion of parts in producung the separation; the tissues relax at the plane 

 of rupture; this ])lane may be near the disk or a variable distances 

 from it on the ray; the ])yloric cieca arc always pulled out and nuich 

 stretched; the break of the caecum occurs at the tube connecting ihv. 

 stoma(!h and glandular portion; the ])yloric (;iecum is gc^ierally taken 

 ])m'k into the arm; the severed ray may live more than a week, even 

 mider adverse circumstances, without signs of regeneration; and, 

 from my experiments extending over a ])eriod of three years, 1 have; 

 found that rays cut various distances from the disk make disks, 

 moutlis and new rays in about six montlis. 



1'jXplanation of Plate XIJI. 



The plate shows growth-series and comets; variabihty in number and size of 

 rays, in size of animal and in breaking places ; color distribution and general 

 characteristics of species; and all except figs. 17 and 18 are as they were found. 

 Fig. 1. — Side view, recently healed. 

 Fig. 2. — Oral view, showing growing down of aboral surface. This also shows 



in fig. 7. 

 Fig. 3. — Oral view, new rays and mouths. 

 Figs. 3-10.— Comets. 



Fig. 11. — Eight new rays, probably two mouths. 

 Figs. 12 and 15. — Five-rayed, showing new arms as "buds." 

 Figs. 14 and 16. — Four-rayed; fig. 16 shows color arrangement. 

 Figs. 17 and 18. — Cut '03 and died '04, a new ray on fig. 17 and a new body on 



fig. 18. 

 Fig. 19. — A large Phataria with 2 madreporites, A and B. 

 Figs. 13 and 20. — Twenty-three six-rayed. 

 Fig. 21. — Shows four distinct break planes and has only one good ray. This 



is a type of the thick specimens. 

 Fig. 23. — Is a type of the thin species. 

 Fig. 22. — Shows two mouth places, A and JJ. 



