194 REPORT ON THE PENXATTTLIDA. 



Krukenberg on the digestive properties of these mesenterial filaments 

 in Sea-anemones, there can be no donbt that these foreign bodies are 

 organisms or portions of organisms which have been swallowed 

 as food and are undergoing digestion. In this case it is of 

 great interest to notice the very marked power possessed by the fila- 

 ments of wrapping themselves around the food particle, so as to attack 

 it, as it were, from all sides at once. The importance of this operation 

 is seen at once from Dr. Krukenberg's account of the act of digestion 

 as being a surface action, only occuring where there is actual contact 

 between the filament and the food particle, and not effected by means 

 of a fluid seci'etiou poured out over the food. 



It is also important to notice that the endodermal cells of the 

 mesenterial filaments mvist in order to effect this enveloping of the 

 food, manifest active changes of form, i.e., must be amoeboid, and tlie 

 fact that those endoderm cells which are specially concerned in 

 digestion are amoeboid has now been established in a considerable 

 number of Codenieratn.* 



In the case of one of the polypes of which we have prepared 

 sections — the third section from the top in Fig. 5 — an additional point 

 of interest has presented itself. Lodged within the polype with its 

 head just at the level of the bottom of the stomach, and its body lying 

 imbedded among the mesenterial filaments, is an Entomostracon. 

 apparently one of those parasitic or semi-parasitic Copepoda in which 

 the jaws are retained in a well developed condition, but the other 

 appendages are rudimentarj'. The ovaries of this Copepoda are in a 

 condition of great activity, containing very numerous ova in various 

 stages of development. Many of the ripe ova have left the parent and 

 are either lying freely in the body-cavity of the jjolype or else are 

 embedded in the mesenterial filaments in the same manner as are the 

 food particles described above. An instance of this is shown in the 

 third section of Fig. 5 at o v, which shows also that the egg after 

 becoming completely embedded in the mesenterial filament has 

 commenced to develope, the stage figured being that in which it has 

 divided into four equal segments. Other eggs from the same 

 specimens have proceeded considerably further in their development. 



It is difficult in this case to determine whether, on the one hand, 

 the Copepod has been swallowed as food and has escaped digestion so 

 far owing to the thick cuticle covering and protecting its body, the 

 eggs being also destined ultimately to serve as food, and being 

 engulphed by the mesenterial filaments for that purpose, but having, 

 owing to their firm investing membrane, not only escaped digestion, 

 but been enabled to develope up to a certain point ; or, on the other 

 hand, whether we are not dealing with a parasitic animal which has 

 planted itself at the bottom of the stomach, so as to intercept the food 



• For a summary of recent observations ou the amcEboid condition of the 

 endoderm in Ccelenterata and other forms, and for important observations ou 

 theprocessof digestion in the fresh-water Medusa Limnococliu in, vide Lankester 

 'On the Intracellular Digestion of Liuinocodium," Quarterly Journal of 

 Microscopic Science, January, 1881. 



