IDYIA ROSEOLA. 



37 



the longitudinal ambulacra, the rows of locomotive flappers extending 

 but little way from the abactinal pole, as is the case in Pleurul)rachia. 

 "We find also the whole spherosome covered with large pigment cells. 



FiR. 56. 



Fig. 57. 



Fig. 65. 



In specimens slightly older, the difference in size between these two 

 sets of tubes becomes more marked in proportion as they become sepa- 

 rated and distinct, as is seen in the two figures, in profile (Fig. 50) and 



Fig. 59. 



Fig. 60. 



Fig. 58. 



from above (Fig. 55). The manner in which the amlndacral tubes are 

 formed, by the drawing uj) into loops of the original chymiferous cavity, 

 is very easily followed in Idyia. It is the same m all the Ctenophora) 



Fig. 55. Fig. 54, seen from the abactinal pole. 



Fig. 56. Somewhat more advanced than Fig. 54, seen from the liroad side. 



Fig. 57. The chymiferous tubes, c', have extended to level of actinostome ; narrow side. 



Fig. 58. The chymiferous tubes, f', have united with the lateral tulus, and formed a circular 

 tube, towards which the short amlndacra, c, are fast |m<Iiing their way. First trace of the ramifi- 

 cations on the long tubes, c'. Figs. 58 -GO are seen from the broad side. 



Fig. 59. The short ambulacra, c, have nearly united with the circular tube ; the spurs of the 

 ambulacra have become more numerous and (juitc prominent. 



Fig. 60. The circuit is now complete between the short and long ambulacra. The spui's or 

 ramifications of the chymiferous tubes are lunuerous, resembling somewliat those of the adult. 



