610 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



irritation be repeated or prolonged ; but if the rod be made to irritate the long basal 

 pinnules all the arms (if the animal be in full vigor) immediately close together 

 with an energy and consentaneousness that are seen in no other movement. 



W. B. Carpenter believed that the ordinary pinnules are especially related to 

 the function of respiration, while the oral pinnules are sensory protective organs. 



Perrier says that in keeping Antedons alive it is necessary to take care to place 

 in the basins rough bodies or twigs, or floating fragments of seaweed, to which 

 they can attach themselves. If this is not done the individuals will attach them- 

 selves to each other and become hopelessly entangled, so that their movements 

 result in mutilation and the consequent mortality may be serious. Moreover, it 

 becomes impossible to remove the dead ones, which become foci of infection. 



By taking these precautions and changing the water in his basins carefully 

 morning and evening, Perrier was able to keep at the same time in the same basin 

 about 50 Antedons in good health. 



The young pentacrinoid larvae accustom themselves to captivity quite as well 

 as the adults. 



Perrier says that the rolling up of the arms in Antedon bifida is an indication 

 of sickness. When the animal is in good health it is generally expanded, and it 

 does not roll up its arms except momentarily when it is disturbed. It likes occa- 

 sionally to leave the stem upon which it is seated and to swim about with con- 

 siderable agility, by means of its arms, which, like graceful oars, alternately strike 

 the liquid. 



When a comatulid has remained with its arms rolled up for some days one 

 may be sure that they will soon drop off. Perrier frequently saw animals, still 

 alive, on which there no longer remained a single arm. Such extensive mutilation 

 soon results in death. 



Studying Antedon adriatica in the aquaria of the zoological station at Trieste 

 Seeliger found that the spermatozoa are ejected in such quantities that only a few 

 males are able to becloud a very considerable amount of water. The release of 

 the spermatozoa is immediately followed by the extension of the eggs, which never 

 appear at any other time. 



At Naples Bury found that the eggs of Antedon mediterranea are always laid, 

 until late in the season, in the morning, probably not much before 8 o'clock. They 

 are attached in masses to the pinnules by a sticky secretion, which makes it ex- 

 tremely difficult to detach them without injury. Each ovum is about 0.3 mm. in 

 diameter and pink in color, and each is inclosed in a transparent and close-fitting 

 vitelline membrane. 



At Trieste Seeliger noted that the extrusion of the genital products of Antedon 

 adriatica always takes place at a very definite hour, about 7 o'clock in the morning. 



Perrier remarked that among the comatulids (Antedon moroccana) sent him 

 from Algiers all the embrj'os on all the pinnules of a given mother were at the 

 same developmental stage. 



Barrois visited Toulon for the purpose of obtaining a series of embryos of 

 Antedon mediterranea of all stages. He collected a large number of animals 

 with embryos, and the next day discovered to his surprise that all the embryos 



