IDYIA ROSEOLA. 



37 



the longitudinal ambulacra, the rows of locomotive flappers extending 

 but little way from the abactinal pole, as is the case in Pleurobrachia. 

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



Fig. 56. 



Fig. 57. 



Fig. 55. 



Iii 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. 56) and 



Fig. 60. 



Fig. 58. 



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

 formed, by the drawing up into loops of the original chymiferous cavity, 

 is very easily followed in Idyia. It is the same in all the Ctenophorse 



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



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



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



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

 tube, towards which the short ambulacra, c, are fast pushing 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 quite prominent. 



Fig. GO. The circuit is now complete between the short and long ambulacra. The spurs or 

 ramifications of the chymiferous tubes are numerous, resembling somewhat those of the adult. 



