STRUCTURE OF THE SEA-ANEMONE. 75 



withdrawn, specimens may be killed expanded by the grad- 

 ual introduction of fresh water, or by plunging them into 

 picric acid. They should then be transferred to the strong- 

 est alcohol, and allowed to soak in it for two or three days 

 until the tissues become hard enough to cut well. Then 

 vertical and transverse sections may be made with a sharp 

 knife. The first fact to observe is, that an alimentary canal 

 is much more clearly indicated than in the Hydrozoa, there 

 being a distinct digestive sac, separate from the body-walls, 

 hanging suspended from the mouth-opening, and held in 

 place by six partitions or septa (mesenteries), which divide 

 the body-cavity into a number of chambers. The digestive 

 sac is not closed, but is open at the bottom of the body, 

 connecting directly with the chambers, so that the chyme, 

 or product of digestion, passes down to the floor of the 

 body, and then into each of the chambers ; thus, by the 

 movements of the cilia lining the body-cavity, the chyme, 

 mixed with the blood, is distributed throughout the body ; 

 this rude mode of circulation being the only means of dis- 

 tribution of the nourishment contained in the circulating 

 fluid, there being no distinct canals, as in the Hydrozoa. 

 These mesenteries may be best studied in a cross-section of 

 the animal after being hardened. It will be found that 

 there are six pairs of complete or primary septa or partitions 

 (mesenteries) which hold the stomach in place, and a num- 

 ber of pairs of shorter ones of unequal length between the 

 complete ones. There are never less than twelve of the 

 secondary partitions, even in the young, and when more 

 numerous they occur in multiples of six (Clark). On the 

 free edges of these shorter mesenteries, which do not extend 

 out to the stomach, there is a mass of long coiled filaments, 

 the mesenterial filaments {craspeda, Fig. 50, cr), which con- 

 tain lasso-cells, situated in a peripheral layer, while the fila- 

 ment is hollow and contains guanin. In dissecting the 

 sea-anemone these mesenterial filaments are always more 

 or less in the way, and have to be carefully removed so as to 

 expose the ovaries and adjoining parts. They press out of 

 the mouth and the cincUdes (small openings through the 



