482 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



to understand without exact knowledge of the physical characters of 

 the medium. Why are the costules more or less salient? Why are 

 the zooecia sometimes in radial series, and sometimes in quincunx? 

 These are some of the questions for study. 



Biology. — Species of ConescJiarellina live with the apex downward 

 and the base upward (Maplestone, 1910). They are attached by 

 extended fine filaments, half an inch long, attached in some cases to 

 tubes of annelids and fragments of shell and issued from pores of 

 the apex. (Whitelegge, 1887, Maplestone, 1910). These radicells 

 must be of an extreme fragility for we have never observed them even 

 on our colonies that have preserved their ectocyst and their chitinous 

 appendages. Perhaps they are perishable and disappear after a 

 certain development of the cone. 



It is hard to understand how a conical colony can maintain its 

 equilibrium even in the water, in a position absolutely inverse to the 

 ordinary laws of statics. One hypothesis is possible to explain this 

 apparent anomaly, namely that of rotation. The small colonies 

 turn without ceasing around their axis and develop their costules 

 in inverse proportion to the facilities which they find to operate 

 this gyratory motion. 



The fixed bryozoa develop their avicularia on their concave por- 

 tions. Conescharellina does the opposite; the avicularia are small 

 and at the bottom of the intercostular furrows for the rotation renders 

 their function absolutely useless. 



The growth in height of the colony is not indefinite; each species 

 appears to have a special maximum height. When this is reached 

 the true base forms with its pores and its small avicularia. During 

 all the time of growth the base presents a porous center surrounded 

 by the radiating zooecia of the last formed ring. The life of these 

 small beings must be precarious and short, for in each species, there 

 is always a large number of colonies that show an incomplete base 

 and do not attain their complete development. Indeed very little 

 is necessary to compromise the stability of this small hydraulic sys- 

 tem. It is at the mercy of a false maneuver of the tentacles or of the 

 avicularia, of an error of architecture of a thread of aberrant water, 

 of a fish that passes or of an obstacle to the rotation. There is no 

 life more strange than that of Flabellopora or ConescJiarellina. They 

 escape the immovable substratum but at the price of a perpetual 

 movement. One dances, the other turns, but in order to flee from 

 the dangerous bottom, in order to escape the immobility, in order 

 to attain the necessary pre} 7 , they construct these complicated boats 

 which human science can imitate but never perfect. 



