5l6 W. B. HARDY. 



On Certain Points in the Structure and Functions of 

 THE Endoderm of Myriothela. 



In any animal three main problems concerning the manipu- 

 lation of its food-stuffs present themselves. These are (1) the 

 disintegration and solution of its food; (2) the absorption of 

 the dissolved or liberated and unchanged material; and (3) 

 the distribution of the products of digestion. We might also 

 add to these the storage of prepared food-stuflF. Many and 

 diverse reasons justify the statement that a cell is hampered 

 or, better, limited in the range of its activity by being loaded 

 with indiflFerent reserve nutriment; and it therefore becomes 

 almost the duty of a special tissue to store material, either as 

 a provision for some extraordinary metabolic effort, or as a 

 consequence of an infrequent and uncertain food-supply. In 

 the case of Myriothela we shall see that this last problem — 

 the storage of reserved nutriment — occupies a large part of 

 the endoderm. 



The disintegration of the food in all animals not possessed 

 of a masticatory apparatus is a process of solution differing 

 only in degree from the final solution of the smaller particles. 

 Yet I think we are justified in speaking of the whole act as a 

 process of disintegration and solution, because of the very 

 general tendency of animals to divide the process into those 

 two stages, and to differentiate the alimentary tract into a 

 special region where disintegration of the food by solution 

 takes place, e. g. the stomach of Vertebrates, and another 

 tract where solution is completed, and where solution and 

 absorption go on hand in hand. 



In an animal of any considerable size the distribution of the 

 products of digestion becomes a problem of the utmost import- 

 ance, not only physiologically, but also from its far-reaching 

 influence on the morphological characters of animals. It has 

 been solved in three main ways : 



1. By the utilisation of the enteric space itself, which func- 

 tions in part as a digestive cavity, and in part as a common 



