250 RITTER AND CROCKER 



the new rays come in in distinct generations, i. e., in sets all the 

 members of which arise simultaneously? If so, do the genera- 

 tions have typically the same number of members, or does the 

 number increase or diminish in succeeding generations? Do 

 the successive rays arise at the same and definite places? With 

 what number of rays does adult life begin? Are the new rays 

 disposed bilaterally? And, perhaps most important of all, is 

 there a ray that corresponds to the ray A of Pycno^odia ? As 

 the author had but six specimens (Perrier, '88) in which new 

 rays were being produced, the material would be inadequate 

 for answering these questions, and future work must supply the 

 information. 



GENERAL REMARKS ON CHARACTERS AND ORIENTATION. 



In Pycnofodia the full-grown stars vary somewhat in the 

 number of rays, having twenty to twenty-four ; but this varia- 

 tion does not depend upon the size of the specimen. The 

 largest individual (R. = 15 cm.) in the museum of the Univer- 

 sity of California had but twenty rays, while others with twenty- 

 two and twenty-four measured 12 and 13 cm. respectively. The 

 number is generally even, twenty, twenty-two, or twenty-four ; 

 but a few specimens with twenty-one have been found. 



While the younger stars show a symmetrical arrangement of 

 rays of different sizes, in only one out of some fifteen adults 

 examined could any distinct inequality be observed. The rays 

 are very equally developed, but so soft and flexible that they 

 appeared to differ in size ; the better the specimens are pre- 

 pared, the more regular in size and arrangement are the rays 

 found to be. 



In order to orient the star, the madreporite is found in each 

 one. It is a fairly large body, but the full development of the 

 papula? often makes a careful search necessary to find it. In 

 young specimens the difficulty is increased by the coloring. 

 Treating the specimens with clearing fluids is of no avail ; but 

 transmitted sunlight brings out the characteristic furrows. At 

 first these are simple, but they increase in complexity of pat- 

 tern with the growth of the star. After finding the madreporite 

 in a few of the smaller animals, it is discovered to hold a defi- 



