NO. 1658. ALCYONARIA OF THE CALIFORNIAN COAST— NUTTING. 597 



main function of the water system in the stem. Water entering the 

 moutlis of the polyps would pass downward into the leaf chambers, 

 which are continuous with the body cavities of the polyps, and thence 

 into the semicircular canals at the bases of the leaves. These canals 

 convey the water to the spongy tissue immediately under the zooid 

 bands of the rachis. Water entering the mouths of the zooids would 

 be conducted immediately to this spongy tissue of the rachis, which 

 freely communicates with the spongy tissue of the stem. From here 

 it could go into the stem chambers and out through the opening at 

 the end of the stem. 



It is quite likely that these currents may be reversed periodically, 

 as is known to be the case in some other coelenterates. The writer 

 was told by one who had observed this species soon after it was taken 

 and placed in a tank that the stem alternately expanded and con- 

 tracted by inhaling .and exhaling water through the opening at the 

 end of the stem, and that the amount of expansion and contraction 

 was very remarkable. That water is taken in through the mouths 

 of the polyps seems very probable, from what is known of the manner 

 of feeding of other polyps. 



In most cases, however, where living polyps have been studied, 

 water is both inhaled and exhaled through the polyp mouth. 



There is doubtless some special and important function pertaining 

 to the zooids in relation to the water system. The great size and 

 number of the cilia in the siphonoglyphs, the regular series of longi- 

 tudinal canals immediately beneath the zooid bands, together with 

 the highly specialized longitudinal muscle bands in that region of 

 the rachis, are hisblv signifi^.a.nt of important service in the life of 

 the oo^onj. 



The present writer has been unable co tmd a datisractory explana- 

 £ion of these interesting structures, but hopes to renew his investiga- 

 tions with living material at no distant time. 



It might be suggested that the contraction of the great longitudinal 

 muscle bands would strongly compress the series of longitudinal 

 water tubes by tending to shorten them, and that the water contained 

 in the canals would find a direct outlet through the mouths of the 

 zooids which would thus serve as excurrent orifices to the colony. 



Jungerson, in his work on the structure and development of Penna- 

 tula jjJi'Osphorea, gives a view of the circulatory system which ascribes 

 an excurrent function to the zooids, but believes that the water from 

 the polyps passes exclusively to the dorsal canal in the stem cavity." 

 This latter statement will certainly not apply to Ptilosarcus quadran- 

 gularis. 



«The present writer has not seen Jungerson's work, but finds it discussed in Traits 

 de Zoologie concrete, Delage and Herouard, II, p. 345. 



