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University of California Publications. 



V.i 



similar case in Metridium, such exceptions may be due to 

 accidental rupture of the foot disk rather than to a normal fission 

 process. 



The third type of fission enumerated was observed by Mrs. 

 Thymic ('59), in what she asserted to be a species of caryophyl- 

 lian coral, though it is questionable whether the corals were not 

 really anemones. According to her account, the eggs of (U/athina 

 smithi, laid in her aquarium, produced polyps which grew to 

 adult size without forming skeletons. It was among such 

 individuals that she obtained the following facts regarding 

 their non-sexual reproduction. The month expands, and the 

 polyp assumes a rectangular shape; the body wall, oeso- 

 phagus, mouth and foot disk between any two adjacent 

 corners break down; the same thing then occurs between the 

 other two corners, dividing the mother into two portion. Each 

 of the latter ordinarily divides again, so that ultimately four 

 pieces, corresponding to the four corners of the rectangle are 

 isolated and become perfect by regeneration. Occasionally but 

 two or three polyps arise from one iu this way. S. ilnrisi 

 reproduces similarly; 8. luciae will probably be found to be in 

 the same categorj . 



Iu every process of reproduction by fission, a period of 

 destruction (fission) can be more or less clearly distinguished 

 from a period of construction (regeneration). In describing the 

 methods of non-sexual reproduction which are associated with 

 the three varieties of longitudinal fission in 8. davisi, it will be 

 convenient to make use of this distinction. 



Fig. 1. The elongated foot disk 

 in an early stage of division, the 

 mesenteries arranged in two sys- 

 tems. From below. 



Fig. 2. Foot disk of dividing polyp 

 from below. Tension indicated by 

 course of mesenteries. 



