240 



C. M. CHILD. 



Cerianthus solitarius, the species which formed the subject of 

 most of the experiments, is considerably smaller than C. inon- 

 branaccus. Owing to the varying degrees of distension and con- 

 traction accurate measurements of the form are difficult to obtain. 

 A considerable number of specimens were measured when 

 apparently fully extended and the body distended with water. 

 These were all among the larger specimens, for the smaller indi- 

 viduals were discarded in nearly all cases. These measurements 

 are of course only approximate and serve merely to indicate the 

 general proportions of the specimens used for experiment. Under 

 other conditions of contraction or distension these same indi- 

 viduals possess very different proportions. In all cases a single 

 individual was measured repeatedly at intervals and the maxi- 

 mum measurements taken as representing complete extension. 

 The foll'owing table presents a few such measurements of different 

 individuals, the measurements being given in millimeters : 



The specimens used were between these limits of size. A com- 

 parison of the measurements of the three individuals shows that 

 the smaller specimen possesses different proportions from the 

 larger, /. c., its transverse diameters are relatively greater as com- 

 pared with the length than those of the larger specimens. In 

 other words, after the individuals reach a certain size further in- 

 crease is chiefly an increase in length. Without giving the fig- 

 ures at this time to prove this point, since it will be taken up 

 later in connection with the discussion of morphallaxis, it may be 

 said that this difference in proportion between small and large 

 specimens is of general and probably universal occurrence in 

 Cerianthus. Smaller specimens are always relatively thicker 

 than large ones. 



In general form the body is nearly cylindrical, expanding or- 

 ally to form the disc and tapering slightly posteriorly. At the 

 aboral end is a small pore which under certain conditions permits 



