352 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



other mesenteries in each polyp remain distinct from those 

 of the other throughout their length. This is a condition 

 one would expect to meet in a case of fission, but not in 

 budding, as will be shown later. 



III. Basal Fragmentation. 



Laceration. — This process has been described for two 

 species of Aiptasia and one species of Bunodes, by Andres, 

 1882. Several cases have come under my notice. On 

 March 29, 1898, two small fragments of a pedal disk were 

 found attached to the side of a dish in which several anem- 

 ones were kept. On April 5th, one of the fragments had 

 disappeared, the other had rounded itself up into the shape 

 of a contracted individual, and possessed a few tentacles. 

 A few days later it had become an apparently well formed 

 individual. The cavit}' in the fragment was a portion of the 

 cavity of the original polyp from which the fragment came. 



On April 5th, the Metridium obtained on September 27th, 

 which was in process of division into three individuals, was 

 found with a gaping wound in the base of the column and 

 foot disk. The large fragment which had been torn from 

 it was near by. It rounded itself up as the others had 

 done. By April 23rd, it had produced two individuals 

 which remained connected by a common base; they had 

 probably arisen independently as buds. By the use of sec- 

 tions their mesenterial systems were seen to be entirely dis- 

 tinct. One individual was diglyphic, the other monoglyphic. 

 There was no sign of a previous connection between any 

 two of these; the directives were distinct throughout. 

 There were six and one-half pairs of complete mesenteries 

 in one individual, six complete and two pairs of incomplete 

 mesenteries in the other. Their arrangement in the latter 

 was according to the formula: — 



Z>-2-Z>'-4-5-6/2-7-8/2. 

 D and D' are the directives. The asymmetry of their posi- 

 tions is noteworthy. It should be noted also that the polyp 

 from which this fragment came was sexually mature and 

 was itself dividing. 



