568 ENTOZOA COLLECTED BY DR WILLEY IX THE WESTERN PACIFIC. 



Fig. 29. Section, slightly oblique through the posterior end of the head of P. diomedeae. 

 The posterior end of the groove of the upper funnel is just visible on the left, the ventral 

 and dorsal water-vascular systems are shown on each side, those on the left approaching 

 to fuse with one another. The strongly marked ridges which separate the right and left 

 suckers are also seen. 



Fig. 30. a. View of Qordius rvilleyi Camer. x 1. 6. Head end x about 10. c. Tail 

 end X about 10. d. The same more highly magnified after Camerano, showing the post-cloacal 

 lamina and the cloacal opening. 



Fig. 31. Youngest known form of Porocephalus tortus Shipley x 10, showing the ringed 

 tail. 



Fig. 32. A side view of a slightly older form of P. tortus x 10, showing an increase 

 in the number of annulations and a hook ; the head is not constricted from the body. 



Fig. 33. A somewhat older form of P. tortus x 2. The head is beginning to separate 

 off from the body, but as yet there are no hooks. The annulations are very marked, and 

 the twisting of the body has not begun. 



Fig. 34. An older form of P. tortus x 2. The neck has appeared and the growth of 

 the reproductive organs has stretched the skin so that the annulations have begun to dis- 

 appear, and the twisting of the body has commenced. 



Fig. 35. The oldest stage, side view of P. tortus x 2. The annulations have completely 

 disappeared, and the twisting of the body is very marked. 



Fig. 36. Ventral view of head, neck and anterior end of trunk of the same. From a 

 sketch by Dr Willey of a live specimen. 



