46 A. C. WALTON 



an arrow head, with three siphonoglyphs, one corresponding to 

 the point of the arrow head, the other two to its barbs, the latter 

 having arisen by a division of one of the original siphonoglyphs. 

 These two specimens, living in the laboratory in a tank of run- 

 ning sea- water, and fed on bits of crushed crab, were kept under 

 observation for almost five weeks. Their development is of 

 especial interest, inasmuch as they showed a slow, but evident, 

 progressive fission longitudinally, which in one case ended in a 

 sudden completion of the process by the ' constriction-and- 

 rupture' method shown by Torrey and Mery ('04) for Metri- 



Fig. 1 Photograph of Actinia A, oral view, showing two separate mouths. 



dium. In Metridium, however, no direct evidence of the fis- 

 sion of the double forms has as yet been recorded. 



When specimen A (fig. 1) was fully expanded, the long axis of 

 its oral disc measured 6.5 cm., and its pedal disc 7.5 cm. As in 

 the case of Metridium, the number of tentacles was greater than 

 normal. The normal number for an adult individual is about 

 one hundred and ten, generally closely corresponding to the 

 number of inter-mesenteric spaces. In this animal, when first 

 found, there were one hundred and eighty-seven tentacles', and 

 two more were formed before fission was completed. The trans- 

 parency of the oral disc allowed the counting of the mesenteries 



